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feed for cake discharge for a minute or two
overall cycle.
in  a  10  to  30  minute
The third type of centrifuge commonly used in sludge dewatering is the
conveyor  type.   Sludge  is fed through a stationary feed pipe into a
rotating bowl in which the solids are settled  out  against  the  bowl
wall  by  centrifugal  force.  From the bowl wall, they are moved by a
screw to the end of the machine, at which point whey  are  discharged.
The  liquid  effluent  is  discharged  through ports after passing the
length of the bowl under centrifugal force.

Application And Performance.  Virtually all industrial waste treatment
systems  producing  sludge  can  use  centrifugation  to  dewater  it.
Centrifugation  is  currently being used by a wide range of industrial
concerns.

The performance of sludge dewatering by centrifugation depends on  the
feed  rate,  the  rotational  velocity  of  the  drum,  and the sludge
composition and concentration.  Assuming proper design and  operation,
the solids content of the sludge can be increased to 20-35 percent.

Advantages   And  Limitations.   Sludge  dewatering  centrifuges  have
minimal  space  requirements  and  show  a  high  degree  of  effluent
clarification.    The  operation  is  simple,  clean,  and  relatively
inexpensive.  The area required for a centrifuge  system  installation
is less than that required for a filter system or sludge drying bed of
equal capacity, and the initial cost is lower.

Centrifuges  have  a  high  power  cost that partially offsets the low
initial cost.  Special consideration must also be given  to  providing
sturdy  foundations  and  soundproofing  because  of the vibration and
noise that result  from  centrifuge  operation.   Adequate  electrical
power  must  also  be  provided  since large motors .are required.  The
major difficulty encountered in the operation of centrifuges has  been
the disposal of the concentrate which is relatively high in suspended,
non-settling solids.

Operational  Factors.  Reliability:  Centrifugation is highly reliable
with proper control of factors such as sludge feed,  consistency,  and
temperature.  Pretreatment such as grit removal and coagulant addition
may  be  necessary,  depending on the composition of the sludge and on
the type .of centrifuge employed.

Maintainability:   Maintenance  consists  of   periodic   lubrication,
cleaning,  and  inspection.   The  frequency  and degree of inspection
required varies depending on the type of sludge solids being dewatered
and the maintenance service conditions.  If the sludge is abrasive, it
is recommended that the first inspection of the rotating  assembly  be
made  after  approximately  1,000 hours of operation.  If the sludge is
                                  227

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not abrasive or   corrosive,   then   the   initial   inspection   might   be
delayed.   Centrifuges  not equipped with a  continuous  sludge  discharge
system require periodic shutdowns  for manual  sludge  cake  removal.

Solid Waste Aspects:  Sludge  dewatered  in the centrifugation process
may be disposed of by landfill.  The clarified effluent  (centrate),  if
high  in  dissolved or  suspended solids,  may  require further  treatment
prior to,discharge.

Demonstration Status.   Centrifugation is currently   used   in  a  great
many  commercial  applications to  dewater sludge.  Work  is underway  to
improve the efficiency,  increase the capacity,  and  lower the  costs
associated with centrifugation.

Coalescing

The  basic  principle of coalescence involves the preferential wetting
of a coalescing medium  by oil droplets  which  accumulate on the  medium
and  then  rise to the  surface of  the solution as they combine to form
larger particles.  The  most  important  requirements  for coalescing
media  are  wettability for  oil and large  surface area.   Monofilament
line is sometimes used  as a coalescing  medium.

Coalescing stages may be integrated with  a  wide variety of gravity oil
separation  devices,  and  some  systems    may    incorporate   several
coalescing  stages.   In  general   a  preliminary oil skimming step  is
desirable to avoid overloading the  coalescer.

One commercially marketed system for  oily  waste  treatment  combines
coalescing  with  inclined  plate   separation and filtration.  In this
system, the oily wastes flow  into an  inclined  plate  settler.   This
unit  consists  of  a stack of inclined baffle plates in  a cylindrical
container with an oil collection chamber  at the top.  The oil droplets
rise and impinge upon the undersides of the plates.  They then migrate
upward to a guide rib which directs the  oil  to  the  oil  collection
chamber, from which oil is discharged for reuse or disposal.

The  oily  water  continues on through  another cylinder containing re-
placeable filter cartridges, which  remove suspended  particles from the
waste.   From there the wastewater enters  a  final cylinder  in which the
coalescing material is  housed.  As  the  oily water passes   through  the
many small, irregular,  continuous passages  in the coalescing material,
the oil droplets coalesce and rise to an oil  collection chamber.

Application  and Performance.   Coalescing is  used to treat oily wastes
which do not separate readily in simple gravity  systems.   The  three
stage  system  described above has achieved effluent concentrations of
10-15 mg/1 oil and grease from raw waste concentrations of  1000  mg/1
or more.
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Advantages and Limitations.  Coalescing allows removal of oil droplets
too  finely  dispersed  for  conventional  gravity separation-skimming
technology.  It also can significantly reduce the residence times  (and
therefore separator volumes) required to  achieve  separation  of  oil
from  some  wastes.   Because  of  its simplicity, coalescing provides
generally high  reliability  and  low  capital  and  operating  costs.
Coalescing   is   not  generally  effective  in  removing  soluble  or
chemically stabilized emulsified oils.  To avoid plugging,  coalescers
must  be  protected  by  pretrea£ment from very high concentrations of
free oil and grease, and suspended  solids.   Frequent  replacement  of
prefilters  may  be  necessary  when  raw waste oil concentrations are
high.

Operational Factors v  Reliability!  Coalescing  is  inherently  highly
reliable since there are no moving parts,, and the coalescing substrate
(monofi lament,  etc.)   is  inert  in  the"  process  and therefore not
subject tp frequent regeneration or replacement  requirements-   Large
loads  or  inadequate pretreatment, however, may result in plugging or
bypass of coalescing stages.

Maintainability: Maintenance requirements  are  generally  limited  to
replacement of the coalescing medium on an infrequent basis.

Solid  Waste  Aspects: No appreciable solid waste is generated by this
process.

Demonstration Status.   Coalescing  has  been  fully  demonstrated  in
industries generating oily wastewater, although none are currently not
in use at any coil coating facility.

Cyanide Oxidation By Chlorine
                           >>,
Cyanide  oxidation  using  chlorine is widely used in industrial waste
treatment to oxidize cyanj.de.  Chlorine can be utilized in either  the
elemental  or  hypochlorite  forms.   This  classic  procedure  can be
illustrated by the following two step chemical reaction:
2.
C12

3C1
                NaCN + 2NaOH = NaCNO + 2NaCl + HO
6NaOH + 2NaCNO = 2NaHCO:i
N
                                                 6NaCl + 2H2O
The reaction presented as equation (2) for the oxidation of cyanate is
the final step in the oxidation of cyanide.  A complete system for the
alkaline chlorination of cyanide is shown in Figure VII-19  (page 280).

The alkaline chlorination process oxidizes cyanides to carbon  dioxide
and  nitrogen.   The  equipment often consists of an equalization tank
followed by two reaction tanks, although the reaction can  be  carried
out in a single tank.  Each tank has an electronic recorder-controller
                                 229

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to  maintain  required  conditions  with  respect  to pH and oxidation
reduction potential (ORP).  In the first reaction tank, conditions are
adjusted to oxidize cyanides to cyanates.   To  effect  the  reaction,
chlorine  is  metered to the reaction tank as required to maintain the
ORP in the range of 350 to 400  millivolts,  and  50  percent ^aqueous
caustic  soda  is  added  to maintain a pH range of 9.5 to 10.  In the
second reaction tank,  conditions are maintained to oxidize cyanate  to
carbon  dioxide  and  .nitrogen.   The  desirable  ORP  and pH for this
reaction are 600 millivolts and a pH of 8.0.   Each  of  the  reaction
tanks  is  equipped  with  a  propeller  agitator  designed to provide
approximately one turnover per minute.  Treatment by the batch process
is accomplished by using two tanks, one for collection of water over a
specified  time  period,  and  one  tank  for  the  treatment  of   an
accumulated  batch.   If  dumps  of  concentrated wastes are frequent,
another tank may be required to equalize the  flow  to  the  treatment
tank.  When the holding tank is full, the liquid is transferred to the
reaction  tank  for  treatment.   After  treatment, the supernatant is
discharged and the sludges are  collected  for  removal  and  ultimate
disposal.
                                 The  oxidation  of  cyanide  waste by
                                                    industrial  plants
Application  and  Performance.
chlorine is a classic process and is found in most
using  cyanide.   This process is capable of achieving effluent levels
that are nondetectable.  The process is potentially applicable to coil
coating facilities where cyanide is a component in conversion  coating
formulations.

Advantages and Limitations.  Some advantages of chlorine oxidation for
handling  process  effluents  are  operation  at  ambient temperature,
suitability  for  automatic  control,  and  low  cost.   Disadvantages
include   the   need   for   careful  pH  control,  possible  chemical
interference in the treatment  of  mixed  wastes,  and  the  potential
hazard of storing and handling chlorine gas.

Operational  Factors.   Reliability:   Chlorine  oxidation  is  highly
reliable with proper monitoring and control, and  proper  pretreatment
to control interfering substances.

Maintainability:   Maintenance  consists of periodic removal of sludge
and recalibration of instruments.
Solid Waste Aspects:
chlorine oxidation.
                      There is no solid waste problem associated  with
Demonstration  Status.  The oxidation of cyanide wastes by chlorine is
a widely used process in plants using cyanide in  cleaning  and  metal
processing baths.
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Cyanide Oxidation By Ozone

Ozone  is a highly reactive oxidizing agent which is approximately ten
times more soluble than oxygen on a weight basis in water.  Ozone  may
be  produced  by  several methods, but the silent electrical discharge
method is predominant in the field.  The silent  electrical  discharge
process  produces  ozone  by  passing oxygen or air between electrodes
separated by an insulating material.  A complete ozonation  system  is
represented in Figure VII-20 (page 281).

Application  and Performance.  Ozonation has been applied commercially
to oxidize cyanides, phenolic chemicals, and  organo-metal  complexes.
Its  applicability to photographic wastewaters has been studied in the
laboratory with good results.   Ozone  is  used  in  industrial  waste
treatment  primarily  to  oxidize  cyanide  to  cyanate and to oxidize
phenols and dyes to a variety of colorless nontoxic products.

Oxidation of cyanide to cyanate is illustrated below:

          CN- + 03 = CNO- + 02

Continued exposure to ozone will convert the cyanate formed to  carbon
dioxide and ammonia; however, this is not economically practical.

Ozone oxidation of cyanide to cyanate requires 1.8 to 2.0 pounds ozone
per  pound of CN-; complete oxidation requires 4.6 to 5.0 pounds ozone
per pound of CN-.   Zinc,  copper,  and  nickel  cyanides  are  easily
destroyed  to  a nondetectable level, but cobalt and iron cyanides are
more resistant to ozone treatment.

Advantages and Limitations.  Some advantages of  ozone  oxidation  for
handling  process  effluents  are its suitability to automatic control
and on-site generation and the fact that  reaction  products  are  not
chlorinated  organics  and  no  dissolved  solids  are  added  in  the
treatment  step.   Ozone  in  the  presence   of   activated   carbon,
ultraviolet,  and  other  promoters shows promise of reducing reaction
time and improving ozone utilization, but the process  at  present  is
limited by high capital expense, possible chemical interference in the
treatment  of  mixed wastes, and an energy requirement of 25 kwh/kg of
ozone generated.  Cyanide is  not  economically  oxidized  beyond  the
cyanate form.

Operational Factors.  Reliability:  Ozone oxidation is highly reliable
with proper monitoring and control, and proper pretreatment to control
interfering substances.

Maintainability:   Maintenance consists of periodic removal of sludge,
and periodic renewal of filters and desiccators required for the input
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of clean dry air; filter life is a function of input concentrations of
detrimental constituents.

Solid Waste Aspects:  Pretreatment to eliminate substances which  will
interfere  with  the  process  may be necessary.  Dewatering of sludge
generated in the ozone oxidation process or in an  "in  line"  process
may be desirable prior to disposal.

Cyanide Oxidation By Ozone With UV Radiation

One  of the modifications of the ozonation process is the simultaneous
application of ultraviolet  light  and  ozxone  for  the  treatment  of
wastewater, including treatment of halogenated organics.  The combined
action   of   these   two  forms  produces  reactions  by  photolysis,
photosensitization, hydroxylation,  oxygenation  and  oxidation.   The
process  is  unique because several reactions and reaction species are
active simultaneously.

Ozonation is facilitated by ultraviolet absorption  because  both  the
ozone  and  the reactant molecules are raised to a higher energy state
so that they react more rapidly.  In addition, free radicals  for  use
in  the  reaction  are  readily  hydrolyzed by the water present.  The
energy and reaction intermediates created by the introduction of  both
ultraviolet  and  ozone  greatly  reduce  the amount of ozone required
compared with a system using ozone alone.  Figure  VII-21  (page  282)
shows a three-stage UV-ozone system.  A system to treat mixed cyanides
requires    pretreatment    that    involves   chemical   coagulation,
sedimentation, clarification; equalization, and pH adjustment.

Application and  Performance.   The  ozone-UV  radiation  process  was
developed  primarily  for  cyanide treatment in the electroplating and
color photo-processing areas.  It has  been  successfully  applied  to
mixed  cyanides  and  organics  from  organic  chemicals manufacturing
processes.  The  process  is  particularly  useful  for  treatment  of
complexed  cyanides  such  as  ferricyanide, copper cyanide and nickel
cyanide, which are resistant to ozone alone.
Ozone combined with UV radiation is a relatively new technology.
units are currently in operation and all four  treat  cyanide  b
waste.
   Four
bearing
Ozone-UV  treatment  could  be  used in coil coating plants to destroy
cyanide  present  in  waste  streams  from  some  conversion   coating
operations.

Cyanide Oxidation By_ Hydrogen Peroxide

Hydrogen peroxide oxidation removes both cyanide and metals in cyanide
containing  wastewaters.   In this process, cyanide bearing waters are
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heated to 49 - 54<>c (120 - 130°F) and the pH is  adjusted  to  10.5  -
11.8.   Formalin  (37 percent formaldehyde) is added while the tank is
vigorously agitated.,   After  2-5  minutes,  a  proprietary  peroxygen
compound  (41 percent hydrogen peroxide with a catalyst and additives)
is added.  After an hour of mixing, the  reaction  is  complete.   The
cyanide  is  converted  to  cyanate and the metals are precipitated as
oxides or hydroxides.  The metals are then removed  from  solution  by
either settling or filtration.

The  main  equipment  required  for  this process is two holding tanks
equipped with heaters and air spargers or mechanical stirrers.   These
tanks  may  be  used  in  a batch or continuous fashion, with one tank
being used for treatment while the other is being filled.  A  settling
tank or a filter is needed to concentrate the precipitate.

Application  and Performance.  The hydrogen peroxide oxidation process
is  applicable  to  cyanidebearing   wastewaters,   especially   those
containing  metal-cyanide  complexes.   In  terms  of  waste reduction
performance, this process can reduce total cyanide to  less  than  0.1
mg/1 and the zinc or cadmium to less than 1.0 mg/1.

Advantages  and  Limitations.  Chemical costs are similar to those for
alkaline  chlorination ' using  chlorine  and  lower  than  those   for
treatment   with   hypochlorite.   All  free  cyanide  reacts  and  is
completely oxidized to the less toxic cyanate state.  In addition, the
metals precipitate and settle quickly, and they may be recoverable  in
many  instances.  However, the process requires energy expenditures to
heat the wastewater prior to treatment.

Demonstration Status.  This treatment process was introduced  in  1971
and  is  used  in  several  facilities.   No  coil  coating plants use
oxidation by hydrogen peroxide.

Evaporation

Evaporation is a concentration process.  Water is  evaporated  from  a
solution,  increasing  the  concentration  of  solute in the remaining
solution.  If the resulting water vapor is condensed  back  to  liquid
water,  the  evaporation-condensation  process is called distillation.
However, to be consistent with industry  terminology,  evaporation  is
used  in this report to describe both processes.  Both atmospheric and
vacuum evaporation are commonly  used  in  industry  today.   Specific
evaporation  techniques  are  shown  in  Figure  VI1-22  (page 283) and
discussed below.

Atmospheric evaporation could be accomplished simply  by  boiling  the
liquid.   However,  to aid evaporation, heated liquid is sprayed on an
evaporation surface, and air is blown  over  the  surface  and  subse-
quently  released  to  the  atmosphere.   Thus,  evaporation occurs by
                                 233

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humidification of the air stream, similar to a drying process.  Equip-
ment for carrying out atmospheric evaporation  is  quite  similar  for
most  applications.   The  major  element is generally a packed column
with an accumulator bottom.  Accumulated wastewater  is pumped from the
base of the column, through a heat exchanger, and back into the top of
the column, where it is sprayed into the packing.  At the  same  time,
air drawn upward through the packing by a fan is heated as it contacts
the hot liquid.  The liquid partially vaporizes and  humidifies the air
stream.   The  fan  then  blows  the  hot,  humid  air  to the outside
atmosphere.  A scrubber is often unnecessary because the packed column
itself acts as a scrubber.

Another form of atmospheric evaporator also works on the  air  humidi-
fication principle, but the evaporated water is recovered for reuse by
condensation.   These air humidification techniques  operate well below
the boiling point of water and  can  utilize  waste  process  heat  to
supply the energy required.

In  vacuum  evaporation,  the evaporation pressure is lowered to cause
the liquid to boil at reduced temperature.  All of the water vapor  is
condensed  and, to, maintain the vacuum condition, noncondensible gases
(air in particular) are removed by a vacuum pump.  Vacuum  evaporation
may  be either single or double effect.  In double effect evaporation,
two  evaporators  are  used,  and  the  water  vapor from  the  first
evaporator  (which  may  be heated by steam) is used to supply heat to
the second evaporator.  As it supplies heat, the water vapor from  the
first   evaporator   condenses.   Approximately  equal  quantities  of
wastewater are evaporated in each unit; thus, the double effect system
evaporates twice the amount of water that a single effect system does,
at nearly the same cost in energy but  with  added   capital  cost  and
complexity.  The double effect technique is thermodynamically possible
because  the second evaporator is maintained at lower pressure (higher
vacuum) and, therefore, lower evaporation temperature.  Another  means
of  increasing  energy  efficiency  is vapor recompression (thermal or
mechanical), which enables heat to be transferred from the  condensing
water   vapor  to  the  evaporating  wastewater.   Vacuum  evaporation
equipment may  be  classified  as  submerged  tube   or  climbing  film
evaporation units.

In  the  most commonly used submerged tube evaporator, the heating and
condensing coil are contained in a single  vessel  to  reduce  capital
cost.  The vacuum in the vessel is maintained by an  eductor-type pump,
which creates the required vacuum by the flow of the condenser cooling
water through a venturi.  Waste water accumulates in the bottom of the
vessel,  and  it is evaporated by means of submerged steam coils.  The
resulting water vapor condenses as it contacts the condensing coils in
the top of the vessel.  The condensate then drips off  the  condensing
coils  into  a  collection  trough  that carries it  out of the vessel.
Concentrate is removed from the bottom of the vessel.
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The major elements of the climbing film evaporator are the evaporator,
separator, condenser, and vacuum pump.  Vifaste water  is  "drawn"  into
the system by the vacuum so that a constant liquid level is maintained
in  the separator.  Liquid enters the steam-jacketed evaporator tubes,
and part of it evaporates so that a mixture of vapor and liquid enters
the separator.  The design of the separator is such that the liquid is
continuously circulated from the separator  to  the  evaporator.   The
vapor  entering  the  separator  flows  out through a mesh entrainment
separator to the condenser, where it is condensed  as  it  flows  down
through the condenser tubes.  The condensate, along with any entrained
air,  is  pumped  out  of the bottom of the condenser by a liquid ring
vacuum pump.  The liquid seal provided by  the  condensate  keeps  the
vacuum in the system from being broken.

Application  and Performance.  Both atmospheric and vacuum evaporation
are used in many industrial plants, mainly for the  concentration  and
recovery of process solutions.  Many of these evaporators also recover
water  for  rinsing.  Evaporation has also been applied to recovery of
phosphate metal cleaning solutions.

In theory, evaporation should yield  a  concentrate  and  a  deionized
condensate.   Actually,  carry-over  has  resulted in condensate metal
concentrations as high as 10 mg/1, although the usual  level  is  less
than  3  mg/1,  pure enough for most final rinses.  The condensate may
also contain organic brighteners and antifoaming agents.  These can be
removed with an activated carbon bed, if necessary.  Samples from  one
plant  showed  1,900  mg/1  zinc  in  the  feed,  4,570  mg/1  in  the
concentrate, and 0.4 mg/1 in the condensate.  Another  plant  had  416
mg/1  copper in the feed and 21,800 mg/1 in the concentrate.  Chromium
analysis for that plant indicated 5,060 mg/1 in the  feed  and  27,500
mg/1  in  the  concentrate.   Evaporators  are available in a range of
capacities, typically from 15 to 75 gph, and may be used  in  parallel
arrangements for processing of higher flow rates.

Advantages and Limitations.  Advantages of the evaporation process are
that  it  permits recovery of a wide variety of process chemicals, and
it is often applicable to concentration or removal of compounds  which
cannot  be accomplished by any other means.  The major disadvantage is
that the evaporation process  consumes  relatively  large  amounts  of
energy  for  the evaporation of water.  However, the recovery of waste
heat  from  many  industrial  processes  (e.g.,   diesel   generators,
incinerators,  boilers  and furnaces) should be considered as a source
of this heat for a totally integrated evaporation  system.   Also,  in
some  cases  solar  heating  could  be  inexpensively  and effectively
applied to evaporation units.  For some explications, pretreatment may
be required to remove solids or bacteria which tend to  cause  fouling
in  the  condenser  or  evaporator.   The  buildup  of  scale  on  the
evaporator surfaces reduces  the  heat  transfer  efficiency  and  may
present a maintenance problem or increase operating cost.  However, it
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has  been  demonstrated that fouling of the heat transfer surfaces can
be avoided or minimized for certain dissolved solids by maintaining  a
seed   slurry   which  provides  preferential  sites  for  precipitate
deposition.   In  addition,  low  temperature   differences   in   the
evaporator   will   eliminate  nucleate  boiling  and  supersaturation
effects.  Steam distillable  impurities  in  the  process  stream  are
carried over with the product water and must be handled by pre or post
treatment.

Operational  Factors.   Reliability:  Proper maintenance will ensure a
high degree of reliability for the system.   Without  such  attention,
rapid  fouling  or deterioration of vacuum^seals may occur, especially
when handling corrosive liquids.

Maintainability:    Operating   parameters   can   be    automatically
controlled.   Pretreatment  may  be 'required,  as  well  as  periodic
cleaning of the system.  Regular replacement of seals, especially in a
corrosive environment, may be necessary.

Solid Waste Aspects:  With only a few exceptions, the process does not
generate appreciable quantities of solid waste.
Demonstration Status.
Evaporation is a fully developed,  commercially
treatment  system.   It  is used extensively to
                                       a  pilot
available  wastewater
recover plating chemicals in the electroplating industry and
scale  unit  has been used in connection with phosphating of aluminum.
Proven performance in silver recovery indicates that evaporation could
be a useful treatment operation for the photographic industry, as well
as for metal finishing.  No data have been reported showing the use of
evaporation in coil coating plants.
Flotation

Flotation is the process of
or oil  to  float  to  the
concentrated  and  removed.
bubbles which attach to the
and causing them to float.
of  sedimentation.   Figure
flotation system.
     causing particles such as metal hydroxides
     surface  of  a  tank  where  they  can  be
       This  is  accomplished  by releasing gas
     solid particles, increasing their buoyancy
     In principle, this process is the opposite
      VI1-23  (page  284)  shows  one  type  of
Flotation  is  used  primarily  in the treatment of wastewater streams
that carry heavy loads of finely  divided  suspended  solids  or  oil.
Solids having a specific gravity only slightly greater than 1.0, which
would  require  abnormally long sedimentation times, may be removed in
much less time by flotation.

This process may be performed in several ways:  foam,  dispersed  air,
dissolved  air,  gravity,  and  vacuum flotation are the most commonly
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used techniques.  Chemical additives are often
performance of the flotation process.
used  to  enhance  the
The  principal  difference  among  types of flotation is the method of
generating the minute gas bubbles (usually air)  in  a  suspension  of
water  and  small  particles.   Chemicals  may  be used to improve the
efficiency with any of the basic methods.   The  following  paragraphs
describe  the  different flotation techniques and the method of bubble
generation for each process.

Froth Flotation - Froth flotation  is  based  on  differences  in  the
physiochemical  properties  in  various  particles.   Wettability  and
surface properties affect the particles' ability to attach  themselves
to gas bubbles in an aqueous medium.  In froth flotation, air is blowri
through  the  solution  containing  flotation reagents.  The particles
with water repellant surfaces stick to air bubbles as  they  rise  and
are  brought  to the surface.  A mineralized froth layer, with mineral
particles attached to air bubbles,  is  formed.   Particles  of  other
minerals which are readily wetted by water do not stick to air bubbles
and remain in suspension.

Dispersed  Air Flotation - In dispersed air flotation, gas bubbles are
generated by introducing the air by means of mechanical agitation with
impellers or by forcing  air  through  porous  media.   Dispersed  air
flotation is used mainly in the metallurgical industry.

Dissolved  Air  Flotation  -  In  dissolved air flotation, bubbles are
produced  by  releasing  air  from  a  supersaturated  solution  under
relatively  high pressure.  There are two types of contact between the
gas bubbles and particles.  The  first  type  is  predominant  in  the
flotation  of  flocculated  materials  and  involves the entrapment of
rising gas bubbles in the flocculated particles as  they  increase  in
size.   The  bond  between  the bubble and particle is one of physical
capture only.   The  second  type  of  contact  is  one  of  adhesion.
Adhesion  results  from  the  intermolecular attraction exerted at the
interface between the solid particle and gaseous bubble.

Vacuum Flotation - This process consists of saturating the waste water
with air either directly in an aeration tank, or by permitting air  to
enter  on  the  suction  of  a  wastewater  pump.  A partial vacuum is
applied, which causes the dissolved air to come  out  of  solution  as
minute bubbles.  The bubbles attach to solid particles and rise to the
surface  to  form  a  scum  blanket,  which  is  normally removed by a
skimming mechanism.  Grit and other heavy solids that  settle  to  the
bottom  are  generally  raked to a central sludge pump for removal.  A
typical vacuum flotation unit consists of a covered  cylindrical  tank
in  which  a  partial vacuum is maintained.  The tank is equipped with
scum  and  sludge  removal  mechanisms.   The  floating  material   is
continuously  swept  to  the  tank periphery, automatically discharged
                                 237

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 into a scum  trough,  and  removed  from  the  unit  by   a   pump   also   under
 partial  vacuum.   Auxilliary  equipment  includes  an  aeration  tank  for
 saturating the wastewater with air, a tank  with a  short  retention time
 for removal  of large bubbles, vacuum  pumps,  and sludge pumps.

 Application  and Performance.   The  primary variables   for flotation
 design  are  pressure,  feed solids concentration, and  retention period.
 The suspended solids in  the effluent  decrease, and the  concentration
 of  solids   in  the   float increases  with increasing  retention period.
 When the flotation process is  used   primarily  for   clarification,   a
 retention  period  of  20 to 30  minutes is  adequate for  separation  and
 concentration.

 Advantages and Limitations.  Some advantages of the flotation  process
 are   the    high   levels   of   solids  separation achieved   in  many
 applications,  the   relatively   low   energy requirements,   and    the
 adaptability to  meet   the  treatment requirements of different  waste
 types.  Limitations  of flotation are  that it often requires   addition
 of  chemicals  to  enhance  process   performance and  that  it generates
 large quantities of  solid waste.

 Operational  Factors.  Reliability:    Flotation  systems  normally  are
 very   reliable  with  proper  maintenance   of  the   sludge collector
 mechanism and the motors and pumps used for aeration.

 Maintainability:  Routine maintenance is  required  on the  pumps  and
 motors.   The  sludge  collector mechanism  is subject to possible cor-
 rosion or breakage and may require periodic replacement.
Solid Waste Aspects:  Chemicals are commonly used to aid the flotation
process by creating a surface or a structure that can easily adsorb or
entrap air bubbles.  Inorganic chemicals, such  as  the  aluminum  and
ferric  salts,  and  activated silica, can bind the particulate matter
together and create a structure that can entrap air bubbles.   Various
organic  chemicals  can  change  the  nature  of either the air-liquid
interface or the solid-liquid interface,  or  both.   These  compounds
usually  collect  on the interface to bring about the desired changes.
The added chemicals plus the particles in solution combine to  form  a
large  volume  of  sludge  which  must  be further treated or properly
disposed.

Demonstration Status.  Flotation is a fully developed process  and  is
readily  available  for  the treatment of a wide variety of industrial
waste streams.

Gravity Sludge Thickening

In the gravity thickening process, dilute sludge is fed from a primary
settling tank or clarifier to a thickening tank where rakes  stir  the
                                 238

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sludge  gently  to  density  it and to push it to a central collection
well.  The supernatant is returned to the primary settling tank.   The
thickened  sludge that collects on the bottom of the tank is pumped to
dewatering equipment or hauled away.  Figure VII-24 (page  285)  shows
the construction of a gravity thickener.

Application   and  Performance.   Thickeners  are  generally  used  in
facilities where the sludge is to be further dewatered  by  a  compact
mechanical device such as a vacuum filter or centrifuge.  Doubling the
solids  content  in  the  thickener  substantially reduces capital and
operating cost of the subsequent dewatering device  and  also  reduces
cost for hauling.  The process is potentially applicable to almost any
industrial plant.

Organic  sludges from sedimentation units of one to two percent solids
concentration can usually be gravity thickened to six to ten  percent;
chemical sludges can be thickened to four to six percent.

Advantages  and  Limitations.   The  principal  advantage of a gravity
sludge thickening  process  is  that  it  facilitates  further  sludge
dewatering.    Other  advantages  are  high  reliability  and  minimum
maintenance requirements.

Limitations of the sludge thickening process are  its  sensitivity  to
the  flow  rate  through  the  thickener  and the sludge removal rate.
These rates must be low enough not to disturb the thickened sludge.

Operational Factors.  Reliability:  Reliability is  high  with  proper
design and operation.  A gravity thickener  is designed on the basis of
square feet per pound of solids per day,  in which the required surface
area  is  related  to  the  solids  entering  and  leaving  the  unit.
Thickener area requirements  are  also  expressed  in  terms  of  mass
loading, grams of solids per square meter per day  (Ibs/sq ft/day).

Maintainability:   Twice  a  year,  a   thickener must be shut down for
lubrication of the drive  mechanisms.   Occasionally,  water  must  be
pumped back through the system in order to  clear sludge pipes.

Solid  Waste  Aspects?   Thickened  sludge  from  a gravity thickening
process will  usually require further  dewatering  prior  to  disposal,
incineration,  or  drying.   The clear  effluent may be recirculated in
part, or  it may  be subjected to further treatment prior to discharge.

Demonstration Status.  Gravity sludge thickeners are  used  throughout
industry  to  reduce  water  content to  a  level where  the sludge may be
efficiently handled.   Further  dewatering   is  usually  practiced  to
minimize  costs  of  hauling   the   sludge  to approved  landfill areas.
Sludge thickening  is used  in seven  coil coating plants.
                                  239

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Insoluble Starch Xanthate

Insoluble starch xanthate  is  essentially  an  ion  exchange  medium  used
to  remove dissolved heavy metals from wastewater.   The water may then
either be reused (recovery application)   or discharged   (end-of-pipe
application).    In  a  commercial  electroplating   operation,  starch
xanthate is coated on a filter medium.  Rinse water  containing dragged
out heavy metals is circulated through the filters and then  reused for
rinsing.  The starch-heavy metal complex  is  disposed of  and replaced
periodically.   Laboratory tests indicate that recovery of metals from
the complex is feasible, with regeneration  of   the  starch  xanthate.
Besides  electroplating,   starch xanthate is potentially applicable to
coil coating, porcelain enameling, copper fabrication, and   any  other
industrial plants where dilute metal wastewater  streams are  generated.
Its present use is limited to one electroplating plant.

Ion Exchange

Ion  exchange is a process in which ions,  held by electrostatic forces
to charged functional groups on the surface  of the ion exchange resin,
are exchanged for ions of  similar charge  from the  solution  in  which
the  resin  is immersed.   This is classified as  a sorption process be-
cause the exchange occurs  on the surface  of  the  resin,  and the  ex-
changing  ion  must  undergo  a  phase transfer  from solution phase to
solid phase.  Thus, ionic  contaminants in a  waste stream  can  be  ex-
changed for the harmless ions of the resin.

Although  the precise technique may vary  slightly according  to the ap-
plication involved, a generalized process description  follows.   The
wastewater  stream being treated passes through  a filter to  remove any
solids, then flows through a cation exchanger which  contains  the  ion
exchange  resin.   Here, metallic impurities such as copper, iron, and
trivalent chromium are retained.  The stream then passes  through  the
anion  exchanger  and  its associated resin.  Hexavalent chromium, for
example, is retained in this stage.  If one  pass does not  reduce  the
contaminant  levels  sufficiently,  the   stream  may  then enter another
series of exchangers.  Many ion exchange   systems  are  equipped  with
more than one set of exchangers for this  reason.

The  other  major portion  of the ion exchange process concerns the re-
generation of the resin, which now  holds those  impurities  retained
from  the  waste  stream.    An  ion exchange unit with in-place regen-
eration is shown in Figure VII-25 (page   286).   Metal  ions  such  as
nickel  are  removed  by   an  acid,  cation  exchange  resin, which is
regenerated with hydrochloric or sulfuric  acid,  replacing   the  metal
ion  with  one  or  more hydrogen ions.   Anions  such as dichromate are
removed by a basic, anion  exchange resin,  which  is  regenerated  with
sodium  hydroxide,  replacing the anion with  one or more hydroxyl ions.
                                 240

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The three principal methods employed by industry for regenerating
spent resin are:
the
A)   Replacement Service:  A regeneration service replaces  the  spent
     resin  with regenerated resin, and regenerates the spent resin at
     its own facility.  The service then has the problem  of  treating
     and disposing of the spent regenerant.

B)   In-Place Regeneration:  Some  establishments  may  find  it  less
     expensive  to  do their own regeneration.  The spent resin column
     is shut down  for  perhaps  an  hour,  and  the  spent  resin  is
     regenerated.   This  results  in  one or more waste streams which
     must be  treated  in  an  appropriate  manner.   Regeneration  is
     performed as the resins require it, usually every few months.

C)   Cyclic Regeneration:  In this process, the  regeneration  of  the
     spent  resins  takes place within the ion exchange unit itself in
     alternating cycles with the ion removal process.  A  regeneration
     frequency  of  twice  an  hour is typical.  This very short cycle
     time permits operation with a very small quantity  of  resin  and
     with  fairly  concentrated solutions/ resulting in a very compact
     system.  Again, this process varies according to application, but
     the regeneration cycle generally begins with caustic being pumped
     through the anion exchanger, carrying  out  hexavalent  chromium,
     for  example, as sodium dichromate.  The sodium dichromate stream
     then passes through a cation  exchanger,  converting  the  sodium
     dichromate  to  chromic acid.  After concentration by evaporation
     or other means, the chromic acid can be returned to  the  process
     line.   Meanwhile,  the  cation  exchanger  is  regenerated  with
     sulfuric acid, resulting in a waste acid  stream  containing  the
     metallic  impurities  removed  earlier.   Flushing the exchangers
     with water completes the cycle.  Thus, the wastewater is purified
     and, in  this  example,  chromic  acid  is  recovered.   The  ion
     exchangers,  with  newly  regenerated  resin,  then enter the ion
     removal cycle again.

Application and Performance.  The  list of pollutants for which the ion
exchange system  has  proven  effective   includes  aluminum,  arsenic,
cadmium,  chromium   (hexavalent and trivalent), copper, cyanide, gold,
iron,  lead, manganese, nickel, selenium, silver, tin, zinc, and  more.
Thus,   it  can  be  applied  to a wide variety of  industrial concerns.
Because of the heavy concentrations of metals  in their wastewater, the
metal  finishing industries utilize ion exchange in several  ways.   As
an  end-of-pipe treatment, ion exchange  is certainly feasible, but its
greatest value is  in recovery applications.  It is commonly used as an
integrated treatment to recover rinse  water   and  process  chemicals.
Some   electroplating  facilities   use   ion exchange to concentrate and
purify plating baths.  Also, many  industrial  concerns,   including   a
                                  241

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number  of  coil   coating  plants,   use   ion   exchange   to  reduce  salt
concentrations  in  incoming water  sources.

Ion exchange  is highly efficient  at   recovering  metal   bearing  solu-
tions.  Recovery of  chromium, nickel, phosphate  solution, and sulfuric
acid from anodizing  is commercial.   A chromic  acid  recovery efficiency
of  99.5 percent has been demonstrated.   Typical data for purification
of rinse water have  been reported.   Sampling at  one coil coating plant
characterized influent and effluent  streams for  an  ion   exchange   unit
on a silver bearing  waste.  This  system was in start-up  at  the time of
sampling, however, and was not found to be operating effectively.
                             Table VII-20
Parameter
     Ion Exchange Performance

     Plant A
                                                    Plant B
All Values mg/1

Al
Cd
Cr+3
Cr+6
Cu
CN
Au
Fe
Pb
Mn
Ni
Ag
SO4
Sn
Zn
Prior To
Purifi-
cation

  5.6
  5.7
  3.1
  7.1
  4.5
  9.8

  7.4

  4.4
  6.2
  1.5

  1.7
 14.8
After
Purifi-
cation

 0.20
 0.00
 0.01
 0.01
 0.09
 0.04

 0.01

 0.00
 0.00
 0.00

 0.00
 0.40
Prior To
 Purifi-
 cation
 After
Purifi-
cation
  43.0
   3.40
   2.30

   1 .70

   1.60
   9.10
 210.00
   1.10
  0.10
  0.09
  0.10

  0.01

  0.01
  0.01
  2.00
  0.10
Advantages  and  Limitations.   Ion exchange is a versatile technology
applicable to a great many situations.  This flexibility,  along  with
its  compact  nature  and  performance,  makes  ion  exchange  a  very
effective method of waste water treatment.   However,  the  resins  in
these  systems  can prove to be a limiting factor.  The thermal limits
of the anion resins, generally in the vicinity of 60°C, could  prevent
its  use in certain situations.  Similarly, nitric acid, chromic acid,
and hydrogen peroxide  can  all  damage  the  resins,  as  will  iron,
manganese,  and  copper when present with sufficient concentrations of
dissolved oxygen.  Removal of a particular trace  contaminant  may  be
uneconomical  because  of the presence of other ionic species that are
                                 242

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preferentially removed.  The regeneration of the resins  presents  its
own problems.  The cost of the regenerative chemicals can be high.  In
addition,  the waste streams originating from the regeneration process
are extremely  high  in  pollutant  concentrations,  although  low  in
volume.  These must be further processed for proper disposal.

Operational  Factors.   Reliability:  With the exception of occasional
clogging or fouling of the resins, ion exchange has  proved  to  be  a
highly dependable technology.

Maintainability:  Only the normal maintenance of pumps, valves, piping
and other hardware used in the regeneration process is required.

Solid  Waste  Aspects:   Few, if any, solids accumulate within the ion
exchangers, and those which do appear are removed by the  regeneration
process.   Proper  prior  treatment  and  planning can eliminate solid
buildup problems altogether.  The brine resulting from regeneration of
the ion exchange resin most usually must be treated to  remove  metals
before discharge.  This can generate solid waste.
Demonstration  Status.
All
for
of  the  applications
commercial  use,  and
mentioned in this
industry  sources
document are  available
estimate  the number of units currently  in the field at well over  120.
The research and development in  ion exchange  is focusing on  improving
the   quality   and   efficiency  of  the  resins,  rather  than  new
applications.  Work is also being done on  a  continuous  regeneration
process whereby the resins are contained on a fluid-transfusible belt.
The  belt  passes  through  a  compartmented  tank  with ion exchange,
washing,  and  regeneration  sections.   The  resins   are   therefore
continually  used  and regenerated.  No  such  system, however,  has  been
reported beyond the pilot stage.

Membrane Filtration

Membrane filtration is a treatment system  for  removing  precipitated
metals  from  a  wastewater  stream.   It must therefore be preceded  by
those treatment techniques which will  properly prepare the  wastewater
for solids removal.  Typically,  a membrane filtration  unit is  preceded
by  pH adjustment  or sulfide addition  for precipitation of the metals.
These steps are followed by the  addition of  a   proprietary   chemical
reagent  which  causes  the  precipitate to  be non-gelatinous, easily
dewatered, and highly stable.  The  resulting mixture of  pretreated
wastewater  and  reagent is continuously recirculated  through  a filter
module and back into a recirculation tank.  The filter module  contains
tubular membranes.   While  the  reagent-metal  hydroxide  precipitate
mixture  flows  through  the   inside   of the tubes, the water and any
dissolved salts permeate the membrane.   When  the  recirculating slurry
reaches  a  concentration of 10  to  15  percent solids,  it  is pumped out
of  the system as sludge.
                                  243

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Application  and  Performance.   Membrane  filtration  appears  to  be
applicable  to  any  wastewater or process water containing metal ions
which can  be  precipitated  using  hydroxide,  sulfide  or  carbonate
precipitation.  It could function as the primary treatment system, but
also   might   find   application  as  a  polishing  treatment  (after
precipitation and settling) to ensure continued compliance with metals
limitations.  Membrane filtration systems are being used in  a  number
of  industrial applications, particularly in the metal finishing area.
They have also been  used  for  heavy  metals  removal  in  the  metal
fabrication industry and the paper industry.

The  permeate  is claimed by one manufacturer to contain less than the
effluent concentrations shown in the following  table,  regardless  of
the   influent   concentrations.    These  claims  have  been  largely
substantiated by the analysis of water samples at  various  plants  in
various industries.

In   the   performance  predictions  for  this  technology,  pollutant
concentrations are reduced to the  levels  shown  below  unless  lower
levels are present in the influent stream.

                                   Table VII-21
                  MEMBRANE FILTRATION SYSTEM EFFLUENT
Specific
Metal
Al
Cr,
Cr
Cu
Fe
Pb
CN
Ni
Zn
TSS
(+6)
(T)
          Manufacturers
          Guarantee
0.5
0.02
0.03
0.1
0.1
0.05
0.02
0.1
0.1
             Plant 19066
            In     Out
                    Plant
                    In
                          31022
                           Out
         0.01
         0.018
         0.043
         0.3
         0.01
 <0.005 <0.005
  9.56   0.017
  2.09   0.046
632      0.1
  0.46
  4. 13
 18.8
288
  0.652
  5.25  <0.005
 98.4    0.057
  8.00   0.222
 21.1    0.263
  0.288  0.01
 <0.005 <0.005
194       0.352
  5.00   0.051
 13.0    8.0
                 Predicted
                 Performai
 0.05
 0.20
 0.30
 0.05
 0.02
 0.40
 0. 10
10.0
Advantages  and  Limitations.   A  major  advantage  of  the  membrane
filtration  system  is  that  installations  can  use  most   of   the
conventional  end-of-pipe  systems  that  may  already  be  in  place.
Removal efficiencies are claimed to be  excellent,  even  with  sudden
variation  of pollutant input rates; however, the effectiveness of the
membrane filtration system can be limited by clogging of the  filters.
Because  pH  changes  in  the  waste stream greatly intensify clogging
problems, the pH must be carefully monitored and controlled.  Clogging
can  force  the  shutdown  of  the  system  and  may  interfere   with
                                 244

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production.   In addition, relatively high capital cost of this system
may limit its use.

Operational Factors.  Reliability:  Membrane filtration has been shown
to be a very  reliable  system,  provided  that  the  pH  is  strictly
controlled.   Improper  pH can result in the clogging of the membrane.
Also, surges in the flow rate of the waste stream must  be  controlled
in  order  to  prevent solids from passing through the filter and into
the effluent.

Maintainability:  The membrane filters must  be  regularly  monitored,
and cleaned or replaced as necessary.  Depending on the composition of
the  waste  stream and its flow rate, frequent cleaning of the filters
may be required.  Flushing with hydrochloric acid for 6-24 hours  will
usually  suffice.   In  addition,  the  routine  maintenance of pumps,
valves, and other plumbing is required.

Solid  Waste  Aspects:   When  the  recirculating  reagent-precipitate
slurry  reaches   10  to   15  percent  solids,  it is pumped out of the
system.  It can then be disposed of  directly  or  it  can  undergo   a
dewatering  process.   Because  this  sludge contains toxic metals,  it
requires proper disposal.

Demonstration Status.  There are  more  than   25  membrane  filtration
systems  presently  in use on metal finishing  and similar wastewaters.
Bench scale and pilot studies  are being run  in an  attempt  to  expand
the  list of pollutants for which  this system  is known to be effective.
Although   there   are no data on the use of membrane  filtration  in  coil
coating plants, the concept has been successfully  demonstrated   using
coil  coating plant wastewater.   A unit has  been  installed  at one  coil
coating plant based on these tests.

Peat  Adsorption

Peat  moss  is  a  complex natural  organic  material  containing  lignin  and
cellulose   as   major   constituents.    These  constituents,  particularly
 lignin,  bear  polar  functional  groups,   such   as   alcohols,   aldehydes,
ketones,   acids,  phenolic hydroxides,  and ethers,  that  can  be involved
 in chemical  bonding.   Because  of  the  polar nature of the material,  its
 adsorption of  dissolved  solids such  as  transition  metals   and  polar
organic molecules is  quite high.   These properties have led to  the use
 of peat as an agent for  the purification of  industrial  wastewater.

 Peat  adsorption  is   a "polishing"  process which can achieve very low
 effluent concentrations  for several  pollutants.   If the concentrations
 of pollutants are above 10 mg/1,  then peat adsorption must be preceded
 by   pH   adjustment   for   metals   precipitation   and   subsequent
 clarification.    Pretreatment  is  also  required  for chromium wastes
 using ferric chloride and sodium  sulfide.   The  wastewater  is  then
                                  245

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pumped into a large metal chamber called a kier which contains a layer
of  peat  through which the waste stream passes.  The water flows to a
second kier for further adsorption.  The wastewater  is then ready  for
discharge.  This system may be automated or manually operated.
             and  Performance.   Peat  adsorption  can be used in coil
             removal  of  residual  dissolved  metals  from  clarifier
Application
coating for
effluent.  Peat moss may be used to treat wastewaters containing heavy
metals such as mercury, cadmium, zinc, copper, iron, nickel, chromium,
and lead, as well as organic matter such as oil, detergents, and dyes.
Peat  adsorption  is currently used commercially at a textile plant, a
newsprint facility, and a metal reclamation operation.

The following table contains performance figures obtained  from  pilot
plant  studies.   Peat  adsorption  was  preceded by pH adjustment for
precipitation and by clarification.

                             Table VII-22
Pollutant
(mg/1)

   Cr+6
   Cu
   CN
   Pb
   Hg
   Ni
   Ag
   Sb
   Zn
                     PEAT ADSORPTION PERFORMANCE
                            In
35,








000
250
36.0
20.0
1 .0
2.5
1 .0
2.5
1 .5
Out
                                                       0.04
                                                       0.24
                                                       0.7
                                                       0.025
                                                       0.02
                                                       0.07
                                                       0.05
                                                       0.9
                                                       0.25
In addition, pilot  plant  studies  have  shown  that  chelated  metal
wastes,  as  well  as  the chelating agents themselves, are removed by
contact with peat moss.
Advantages and  Limitations.   The  major  advantages  of  the  system
include  its  ability to yield low pollutant concentrations, its broad
scope in terms of the  pollutants  eliminated,  and  its  capacity  to
accept wide variations of waste water composition.

Limitations  include the cost of purchasing, storing, and disposing of
the peat moss; the necessity for regular replacement of the  peat  may
lead to high operation and maintenance costs.  Also, the pH adjustment
must be altered according to the composition of the waste stream.
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Operational   Factors.     Reliability;   The  question  of  long  term
reliability is not yet  fully  answered.   Although  the  manufacturer
reports  it  to  be  a highly reliable system, operating experience is
needed to verify the claim.

Maintainability:  The peat moss used  in this process soon exhausts its
capacity to adsorb pollutants.   At   that  time,  the  kiers  must  be
opened, the peat removed, and fresh peat placed inside.  Although this
procedure  is  easily  and  quickly   accomplished,  it must be done at
regular intervals, or the system's efficiency drops drastically.

Solid Waste Aspects:  After removal from the kier, the spent peat must
be eliminated.   If incineration is used, precautions should  be  taken
to   insure  that  those  pollutants   removed  from  the  water are not
released again  in the combustion process.  Presence of sulfides  in the
spent peat, for  example, will give rise to sulfur dioxide  in the fumes
from burning.   The presence of significant quantities of   toxic  heavy
metals  in  coil  coating  manufacturing  wastewater  will   in general
preclude  incineration of peat used in treating  these wastes.

Demonstration Status.  Only three facilities  currently use  commercial
adsorptionsystems   in  the  United States -  a  textile manufacturer,  a
newsprint  facility,  and  a  metal reclamation firm.  No data  have  been
reported  showing the use of peat  adsorption  in  coil  coating  plants.

Reverse Osmosis

The  process  of  osmosis   involves   the  passage of  a  liquid through a
semipermeable membrane  from a dilute  to a more  concentrated  solution.
Reverse  osmosis  (RO)  is  an  operation in which pressure is applied to
 the more   concentrated   solution,   forcing  the  permeate  to  diffuse
 through  the membrane   and  into  the  more  dilute  solution.    This
 filtering action produces  a concentrate and  a  permeate  on  opposite
 sides of  the membrane.   The concentrate can then be further treated or
 returned   to  the  original  operation  for  continued  use, while the
 permeate  water  can be recycled for use as clean water.   Figure  VI1-26
 (page 287) depicts a reverse osmosis system.

 As  illustrated  in  Figure  VII-27   (page 288), there are three basic
 configurations used in commercially  available  RO  modules:   tubular,
 spiral-wound, and hollow fiber.   All of these operate on the principle
 described  above,  the  major  difference  being  their mechanical and
 structural design characteristics.

 The tubular membrane module  uses  a porous  tube  with  a  cellulose
 acetate membrane-lining.  A common tubular module consists of a length
 of  2.5  cm  (1  inch)  diameter  tube wound on a supporting spool and
 encased in a plastic shroud.  Feed water is driven into the tube under
 pressures varying from 40 - 55 atm (600-800 psi).  The permeate passes
                                   247

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 through the walls of the tube and is collected in a manifold while the
 concentrate is drained off at the end of the tube.   A less widely used
 tubular RO module uses a straight tube contained in a  housing,   under
 the same operating conditions.

 Spiral-wound  membranes consist of a porous backing sandwiched between
 two cellulose acetate membrane sheets and bonded  along  three  edges
 The fourth edge of the composite sheet is attached  to a large permeate
 collector tube.   A spacer screen is then placed on  top of the membrane
 sandwich  and  the entire stack is rolled around the centrally located
 tubular permeate collector.   The rolled up package  is inserted into  a
 pipe  able  to withstand the high operating pressures employed in this
 process,  up to 55 atm (800 psi)  with the  spiral-wound  module.    When
 the  system  is operating,  the  pressurized product  water permeates the
 membrane and  flows  through  the  backing  material  to  the  central
 collector  tube.    The  concentrate  is  drained off at the end  of the
 container pipe and can be reprocessed or  sent  to   further  treatment
 facilities.

 The  hollow  fiber  membrane  configuration  is made up of  a bundle ot
 polyamide fibers  of approximately 0.0075 cm (0.003  in.)  OD  and  0.0043
 cm   (0.0017   in.)   ID.    A  commonly used hollow fiber module contains
 several  hundred  thousand of  the  fibers placed  in a  long tube,  wrapped
 around   a  flow  screen,  and  rolled into a spiral.   The fibers are bent
 in  a  U-shape and  their ends  are   supported  by  an   epoxy  bond.    The
 hollow   fiber  unit is operated  under 27 atm (400 psi),  the feed  water
 being dispersed  from  the  center  of  the  module   through  a porous
 distributor   tube.    Permeate flows  through the membrane to the hollow
 interiors of the  fibers  and  is collected at the ends of  the fibers.

 The hollow fiber  and spiral-wound modules have  a   distinct  advantage
 over  the  tubular   system   in that  they are able to load a very  large
 membrane  surface  area into a relatively  small  volume.   However,   these
 two   membrane types  are much   more  susceptible  to  fouling  than  the
 tubular system, which  has a  larger flow  channel.  This   characteristic
 also  makes   the   tubular membrane much  easier  to clean  and regenerate
 than  either   the   spiral-wound   or    hollow   fiber   modules      One
manufacturer   claims    that  their   helical   tubular  module  can  be
physically wiped  clean by passing  a   soft   porous   polyurethane  pluq
under pressure through the module.

Application   and Performance.  In a number .of metal  processing plants
the overflow  from   the   first  rinse   in  a  countercurrent  setup  is
directed   to  a  reverse  osmosis unit,  where  it is  separated  into  two
streams.   The concentrated stream contains dragged out   chemicals   and
is  returned  to  the  bath  to   replace  the   loss of solution due to
evaporation and dragout.  The dilute  stream  (the permeate)   is  routed
to  the   last  rinse  tank to provide water  for the rinsing operation.
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The rinse flows from the last tank to the first tank and the cycle
complete.
is
The  closed-loop  system  described  above  may be supplemented by the
addition of a vacuum evaporator after the RO unit in order to  further
reduce  the  volume  of  reverse  osmosis concentrate.  The evaporated
vapor can be condensed and returned to the last rinse tank or sent  on
for further treatment.

The largest application has been for the recovery of nickel solutions.
It  has been shown that RO can generally be applied to most acid metal
baths with a high degree of performance, providing that  the  membrane
unit  is  not  overtaxed.   The limitations most critical .here are the
allowable pH range and maximum operating pressure for each  particular
configuration.   Adequate prefiltration is also essential.  Only three
membrane types are readily available in commercial RO units, and their
overwhelming use has been for  the  recovery  of  various  acid  metal
baths.  For the purpose of calculating performance predictions of this
technology,  a  rejection ratio of 98 percent is assumed for dissolved
salts, with 95 percent permeate recovery.

Advantages and Limitations.  The major advantage  of  reverse  osmosis
for  handling  process  effluents is its ability to concentrate dilute
solutions  for  recovery  of  salts  and  chemicals  with  low   power
requirements.   No  latent  heat of vaporization or fusion is required
for effecting separations; the main energy requirement  is for  a  high
pressure pump.  It requires relatively little floor space for compact,
high capacity units, and  it exhibits good recovery and  rejection rates
for  a  number  of  typical  process  solutions.   A  limitation of the
reverse osmosis process for treatment  of  process  effluents  is  its
limited  temperature  range for satisfactory operation.  For cellulose
acetate systems, the preferred limits are 18° to 30°C  (65°  to  85°F);
higher  temperatures will  increase the rate of membrane hydrolysis and
reduce system life, while  lower temperatures will result  in  decreased
fluxes  with  no  damage   to  the  membrane,,   Another  limitation   is
inability  to  handle  certain  solutions.   Strong  oxidizing  agents,
strongly   acidic  or  basic  solutions,  solvents,  and other organic
compounds  can cause dissolution of the membrane.   Poor rejection   of
some  compounds  such  as  borates and low molecular weight organics  is
another problem.  Fouling  of membranes by slightly soluble  components
in solution or colloids  has caused  failures, and fouling of membranes
by feed waters with high  levels of suspended solids can be a  problem.
A final  limitation  is  inability to treat or achieve high  concentration
with  some  solutions.  Some concentrated  solutions may have  initial os-
motic  pressures  which   are so high  that they either exceed  available
operating  pressures or are uneconomical  to  treat.
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 Operational Factors.   Reliability:   Very good reliability is  achieved
 so long as the proper precautions are taken to minimize the chances of
 fouling  or  degrading  the membrane.   Sufficient testing of the waste
 stream  prior  to  application  of   an  RO  system  will  provide  the
 information needed to insure a successful application.

 Maintainability:    Membrane life is estimated to range  from six months
 to three years,  depending on the use of the  system.    Down  time  for
 flushing  or cleaning is on the order of 2 hours as often as once each
 week;  a substantial portion of  maintenance  time  must  be  spent  on
 cleaning any prefilters  installed ahead of the reverse  osmosis unit.

 Solid   Waste Aspects:   In a closed  loop system utilizing RO there is a
 constant recycle of concentrate and a minimal amount  of  solid  waste'.
 Prefiltration  eliminates many solids before they reach the module and
 helps  keep the buildup to a  minimum.    These  solids  require  proper
 disposal.                                                        v  *

 Demonstration  Status.    There  are  presently  at  least  one hundred
 reverse osmosis  waste water applications in a variety  of  industries.
 In addition  to   .these,  there are  thirty to forty units being used to
 provide pure process  water for several  industries.  Despite  the  many
 types  and  configurations  of membranes,  only the spiral-wound cellulose
 acetate   membrane   has    had   widespread   success   in  commercial
 applications.

 Sludge Bed Drying

 As  a waste treatment  procedure,   sludge  bed  drying  is  employed  to
 reduce  the  water content of a  variety of sludges to  the point where
 they are amenable  to  mechanical  collection and  removal   to  landfill
 These  beds usually consist of  15  to 45  cm (6 to 18  in.)  of sand  over  a
 30  cm  (12 in.) deep  gravel drain  system made up of  3  to 6 mm (1/8  to
 1/4 in.) graded gravel overlying  drain   tiles.    Figure   VII-28   (page
 289) shows the construction of a  drying bed.

 Drying  beds  are usually divided  into sectional  areas  approximately 7  5
 meters   (25   ft)   wide  x   30   to 60 meters (100  to 200  ft)  long.   The
 partitions  may be  earth embankments, but  more  often are  made  of  planks
 and supporting grooved posts.

 To apply liquid sludge to  the  sand  bed,  a closed  conduit  or  a  pressure
pipeline with  valved  outlets  at   each   sand   bed  section   is   often
 employed.   Another  method  of  application   is  by  means of an  open
 channel with  appropriately  placed side  openings which  are controlled
by  slide   gates.   With   either  type  of  delivery system, a  concrete
splash slab should be provided  to  receive  the  falling   sludge  and
prevent erosion of the sand surface.
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Where  it  is  necessary to dewater sludge continuously throughout the
year regardless of the weather, sludge beds  may  be  covered  with  a
fiberglass  reinforced  plastic  or  other  roof.  Covered drying beds
permit a greater volume of sludge drying per  year  in  most  climates
because  of  the  protection afforded from rain or snow and because of
more efficient control of temperature.  Depending on  the  climate,  a
combination of open and enclosed beds will provide maximum utilization
of the sludge bed drying facilities.

Application  and  Performance.   Sludge  drying  beds  are  a means of
dewatering sludge from clarifiers and  thickeners.   They  are  widely
used both in municipal and industrial treatment facilities.

Dewatering of sludge on sand beds occurs by two mechanisms: filtration
of  water  through  the  bed   and  evaporation of water as a result of
radiation and convection.  Filtration is generally complete in one  to
two  days  and may result in solids concentrations as high as  15  to 20
       •*   _      .   __._.  ..    ••     -*     • •    T ___?._ 	 l_ J T • J	  ,_> .C" £_l_.A
percent.
sludge.
The rate of filtration depends on the  drainability  of  the
The   rate  of  air  drying  of  sludge  is  related to temperature,  relative
humidity,  and  air  velocity.   Evaporation will proceed  at  a  constant
rate   to   a  critical   moisture   content,  then at a falling rate to an
equilibrium moisture content.  The   average  evaporation  rate  for  a
sludge is  about  75 percent of that  from a free water surface.

Advantages and  Limitations.   The main advantage of sludge drying beds
over  other types of sludge dewatering  is the relatively  low  cost  of
construction,  operation,  and maintenance.

Its   disadvantages are the  large area  of land required and long drying
times that depend, to  a great extent,  on climate and weather.

Operational Factors.   Reliability:   Reliability is high with favorable
climactic  conditions,  proper bed design and care to avoid excessive or
unequal sludge application.   If  climatic conditions in  a  given  area
are  not favorable  for  adequate drying, a cover may be necessary.

Maintainability:   Maintenance  consists basically of periodic removal
of the dried  sludge.   Sand  removed from the drying bed with the sludge
must be replaced and the sand layer resurfaced.

 The  resurfacing of sludge beds is the major expense item in sludge bed
 maintenance,  but there are  other areas which  may  require  attention.
 Underdrains   occasionally  become  clogged  and  have  to  be cleaned.
 Valves or sludge gates that control the flow of  sludge  to  the  beds
 must  be  kept  watertight.   Provision for drainage of lines in winter
 should be provided to prevent damage from  freezing.   The  partitions
 between  beds  should  be  tight so that sludge will not flow from one
                                  251

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 compartment to another.   The outer walls
 should also be watertight.
or  banks  around  the  beds
 Solid  Waste  Aspects:    The  full  sludge  drying  bed must either be
 abandoned or the collected solids  must  be  removed  to  a  landfill
 These  solids  contain  whatever metals or other materials were settled
 in the clarifier.   Metals  will  be  present  as  hydroxides,   oxides,
 sulfides,   or  other salts.   They have the potential for leaching and
 contaminating ground water,  whatever the  location  of  the  semidried
 solids.    Thus  the abandoned bed or landfill should include provision
 for runoff control and  leachate monitoring.

 Demonstration Status.   Sludge beds have been in  common  use  in  both
 municipal    and   industrial   facilities  for  many  years.    However
 protection of ground water from contamination is not always adequate.

 Ultrafiltration

 Ultrafiltration (UF)  is a process which uses  semipermeable polymeric
 membranes  to separate emulsified or colloidal materials suspended in a
 liquid phase  by   pressurizing  the  liquid  so that it permeates the
 membrane.   The membrane of an ultrafilter  forms  a  molecular  screen
 which  retains molecular particles based on  their differences  in size
 shape, and  chemical  structure.    The  membrane  permits  passage  of
 solvents   and  lower  molecular  weight  molecules.    At  present,   an
 ultrafilter is capable  of removing materials with molecular  weights in
 the range  of 1,000 to 100,000 and particles  of  comparable  or  larger
 sizes.

 In   an  Ultrafiltration process,  the feed solution is pumped through a
 tubular membrane unit.   Water and some low molecular weight  materials
 pass   through  the membrane   under  the applied pressure of 10  to 100
 psig.  Emulsified  oil droplets and suspended particles  are  retained
 concentrated,   and removed   continuously.    In   contrast  to  ordinary
 filtration,  retained materials are  washed  off   the  membrane  filter
 r?!r  £•-, !rha!?.   Sld by   ifc'    Figure  VII-29 (page 290)  represents  the
 Ultrafiltration process.

 Application    and   Performance.     Ultrafiltration    has   potential
 application  to  coil coating plants for  separation  of  oils and  residual
 solids  from  a variety   of   waste streams.   In  treating coil coatinq
wastewater   its greatest  applicability   would   be   as   a  polishing
 treatment  to   remove   residual   precipitated  metals  after   chemical
precipitation  and  clarification.   Successful  commercial  use,   however
has  been primarily for separation of emulsified oils  from wastewater
Over one hundred such units now operate  in the United  States,  treating
emulsified oils from a  variety of  industrial processes.   Capacities  of
currently operating units  range from a  few hundred gallons a  week   to
50,000 gallons per day.   Concentration  of oily emulsions  to  60 percent
                                 252

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oil  or more are possible.  Oil concentrates of 40 percent or more are
generally suitable for incineration, and the permeate can  be  treated
further  and in some cases recycled back to the process.  In this way,
it is possible to eliminate contractor removal costs for oil from some
oily waste streams.

The following test data   indicate  ultrafiltration  performance  (note
that UF is not intended to remove dissolved solids):

                             Table VII-23

                     ULTRAFILTRATION PERFORMANCE
Parameter

Oil  (freon extractable)
COD
TSS
Total Solids
Feed (mg/1)

   1230
   8920
   1380
   2900
Permeate (mg/1)

       4
     148
      13
     296
The  removal percentages shown are  typical,  but  they  can  be  influenced
by pH and other conditions.

The permeate or effluent from the ultrafiltration  unit  is normally   of
a  quality that can be reused in industrial  applications  or  discharged
directly.  The  concentrate  from   the   ultrafiltration  unit   can   be
disposed of as any oily or solid waste.
Advantages    and    Limitations.
        Ultrafiltration
       is
	   	   	                           sometimes  an
attractive alternative to chemical treatment because of lower  capital
equipment,  installation,  and  operating  costs,  very  high  oil and
suspended solids removal, and little required pretreatment.  It places
a positive barrier between pollutants arid effluent which  reduces  the
possibility  of extensive pollutant discharge due to operator error or
upset in settling and skimming systems.  Alkaline values  in  alkaline
cleaning solutions can be recovered and reused in process.

A  limitation of ultraf iltration for treatment of process effluents is
its narrow temperature range (18° to 30°C) for satisfactory operation.
Membrane life decreases with higher temperatures, but  flux  increases
at  elevated temperatures.  Therefore, surface area requirements are a
function of temperature and become a tradeoff  between  initial  costs
and  replacement costs for the membrane.,  In addition, ultraf iltration
cannot handle certain solutions.  Strong oxidizing  agents,  solvents,
and  other  organic  compounds  can dissolve the membrane.  Fouling is
sometimes a problem, although the  high  velocity  of  the  wastewater
normally  creates  enough  turbulence  to  keep  fouling at a minimum.
Large solids particles can sometimes puncture the membrane and must be
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removed by  gravity  settling  or  filtration  prior  to  the  ultraf iltration
unit.

Operational   Factors.    Reliability:     The    reliability    of     an
ultrafiltration system  is dependent on  the proper filtration,  settling
or  other treatment of  incoming waste streams  to prevent  damage to  the
membrane.   Careful  pilot studies should be done  in   each   instance   to
determine   necessary pretreatment steps and  the  exact membrane type to
be used.

Maintainability;  A limited  amount of regular  maintenance is   required
for  the  pumping system.  In addition,  membranes must  be periodically
changed.  Maintenance associated with membrane plugging can be reduced
by selection of a membrane with optimum physical  characteristics   and
sufficient  velocity  of  the   waste stream.   It is  often necessary to
occasionally pass a detergent solution  through the system to remove an
oil and grease film which accumulates on the   membrane.    With proper
maintenance membrane life can be greater than  twelve months.
    d  Waste  Aspects;   Ultrafiltration   is used primarily to recover
solids and liquids-.   It therefore eliminates solid waste problems when
the solids (e.g., paint  solids)  can  be  recycled  to  the  process.
Otherwise, the stream containing solids must be treated by end-of-pipe
equipment.   In the most probable applications within the coil coating
category, the ultrafilter  would  remove   hydroxides  or  sulfides  of
metals which have recovery value.

Demonstration  Status.   The ultrafiltration process is well developed
and commercially available for treatment of wastewater or recovery  of
certain high molecular weight liquid and solid contaminants.

Vacuum Filtration

In wastewater treatment plants, sludge dewatering by vacuum filtration
generally  uses  cylindrical  drum filters.  These drums have a filter
medium which may be cloth made of natural  or  synthetic  fibers  or  a
wire-mesh  fabric.  The drum is suspended  above and dips into a vat of
sludge.  As the drum  rotates slowly,  part  of  its  circumference  is
subject  to an internal vacuum that draws  sludge to the filter medium.
Water is drawn through the porous filter cake to a discharge port, and
the dewatered sludge, loosened by compressed air, is scraped from  the
filter  mesh.   Because  the dewatering of sludge on vacuum filters is
relativley expensive per kilogram of water removed, the liquid  sludge
is frequently thickened prior to processing.   A vacuum filter is shown
in Figure VII-30 (page 291).
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Application  and Performance.  Vacuum filters are frequently used both
in municipal treatment plants and in a  wide  variety  of  industries.
They  are  most  commonly  used in larger facilities, which may have a
thickener to double the solids -content  of  clarifier  sludge  before
vacuum filtering.

The  function  of  vacuum filtration is to reduce the water content of
sludge, so that the solids content increases from about 5  percent  to
about 30 percent.

Advantages  and  Limitations.   Although  the  initial  cost  and area
requirement of the vacuum filtration system are higher than those of a
centrifuge, the operating cost is lower, and no special provisions for
sound and vibration protection need be  made.   The  dewatered  sludge
from  this  process   is  in  the  form  of  a  moist  cake  and can be
conveniently handled.

Operational Factors.  Reliability:  Vacuum filter systems have  proven
reliable  at  many  industrial and municipal treatment facilities.  At
present, the largest  municipal installation is at the  West  Southwest
waste  water  treatment  plant  of  Chicago,  Illinois, where 96  large
filters were installed in 1925, functioned approximately 25 years, and
then were replaced with  larger  units.   Original  vacuum  filters  at
Minneapolis-St.  Paul,   Minnesota now have over 28 years of continuous
service, and Chicago  has some units with similar  or  greater  service
life.

Maintainability:   Maintenance consists of the cleaning or replacement
of  the filter media,  drainage grids, drainage piping, filter pans, and
other parts of  the equipment.  Experience  in a number of vacuum filter
plants indicates that maintenance  consumes  approximately  5  to   15
percent of  the  total  time.   If carbonate buildup  or  other problems are
unusually   severe, maintenance time may be as high as 20 percent.  For
this reason, it  is desirable to maintain one or more spare units.

If  intermittent  operation  is used,  the  filter   equipment  should   be
drained and washed each  time it  is  taken out of service.  An allowance
for this wash  time must  be  made  in  filtering schedules.

Solid  Waste   Aspects:   Vacuum  filters generate  a solid  cake which  is
usually trucked directly to landfill.  All   of  the  metals  extracted
from   the   plant wastewater  are   concentrated   in  the  filter  cake  as
hydroxides, oxides,  sulfides,  or other salts.

Demonstration  Status. Vacuum filtration  has  been widely  used  for many
years.   It  is  a  fully  proven,   conventional   technology   for   sludge
dewatering.
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 IN-PLANT TECHNOLOGY

 The  intent   of   in-plant technology for the coil  coating point source
 category  is   to  reduce  or   eliminate  the  waste   load   requiring
 end-of-pipe   treatment   and  thereby  improve  the  efficiency  of   an
 existing waste treatment system or  reduce the requirements  of  a  new
 treatment system.    In-plant  technology  involves  improved rinsing,
 water  conservation,  process bath conservation,  reduction   of  dragout,
 automatic controls,  good housekeeping practices, recovery and reuse of
 process   solutions,  process modification and waste treatment.   The  in-
 plant  technology has been divided into two areas:

           In-process treatment and  controls
           Process substitutions

 In-Process Treatment and Controls

 In-process treatment and controls can apply to  both existing  and  new
 installations  and use technologies  and methodologies that have already
 been   developed.    Coil   coating operations  consist  of  three main
 functional groups;  cleaning,  conversion coating and painting.   Each of
 these  operations is  amenable  to reduction of both  chemical   and  water
 usage.    These  reductions  in  chemical  and water usage  are desirable
 because  of the  attendant  reductions  in  pollutant  discharge  which
 results   from  treating   smaller volumes  of  more concentrated waste
 streams.

 A major  portion  of  the oil, grease,  dirt  and oxide coating  is   removed
 from   the  coil by alkaline  cleaning  and rinsing.   Cleaning  of  the coil
 is  extremely important because imcomplete cleaning  adversely   affects
 subsequent operations.   The   primary  factors that adversely affect
 cleaning and rinsing efficiency are:

     Incorrect alkaline  cleaning compound for basis material.
     Incorrect temperature  of  alkaline  cleaning   solution   and  rinse
     water.
     Insufficient number  of spray nozzles or insufficient pressure  for
     both  alkaline cleaning and rinsing.
     Insufficient squeegee  action  to  prevent  excessive   dragout   of
     alkaline  cleaning solution.
     Absence of  bath  equilibrium controls that  automatically add  make-
     up water and cleaning  solution.
     Undefined soils
     Insufficient time

Alkaline   cleaning   solutions   are   formulated  for    specific    basis
materials.   For  example,  the   cleaning   compound   for steel  is more
alkaline than for galvanized or  aluminum.   The  most  advanced  alkaline
cleaning solutions contain phosphates  that  form soluble complexes with
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the  dissolved  basis  materials rather than an insoluble sludge.  The
formation of  an  insoluble  sludge  may  necessitate  discarding  the
solution before exhausting all available alkalinity.

Operating  temperature is as important as the proper alkaline cleaning
solution and concentration.  A solution that is too cold  may  not  be
able  to  dissolve either enough of the dry alkaline cleaning compound
or the dirt, oil, grease and oxides from the coil.  A solution that is
too warm may set certain types of soil onto the coil  itself,  in  the
spray  nozzles,  or onto the tank.  In addition, excessive temperature
may cause excessive foaming.

Spray nozzles and pressures should be adequate to  assure  overlapping
coverage  of the work area.  Experience will dictate how fast the coil
can move and be effectively cleaned with a given set of spray  nozzles
and pressure.

Following  the  alkaline  cleaning,  squeegees are  important to  reduce
dragout of the alkaline cleaning compounds.  Excessive dragout reduces
the rinsing rate and  wastes  cleaning  materials.   Of  the  thirteen
visited  plants,  ten have dragout control in the form of squeegees or
air knives somewhere in the line.  Automatic  alkalinity  sensors  can
reduce  the  consumption  of  alkaline  cleaning compounds; six  of the
visited plants used automatic controls to maintain  bath equilibrium.

The use of alkaline cleaning rinse water as make-up to  the  alkaline
cleaning   tank   can   conserve   water.   Another  applicable  water
conservation mechanism   (particularly  for  new   installations)  is   a
countercurrent   rinse.  This system uses only one fresh water feed for
the entire set of tanks,  and  it  is introduced  in  the last tank of  the
arrangement.   The  overflow  from  each tank becomes the feed for the
tank  preceding it.  Thus,  the concentration of  contaminants  decreases
rapidly  from  the  first  to   the  last   tank.   Two stage rinsing can
achieve a 30 to  1 reduction  in  water  requirements while  3  stages  can
reduce   flow    100  to   1   for   the   same  cleanliness  requirements.
Countercurrent rinses  can be  used  at   coating   plants  and   are  quite
common  in the  electroplating  industry.

The   conversion   coating   function  is  the   heart  of the  coil  coating
operation.   This is one  of  the  steps  in  which  material  is  added  to the
coil.   The  three types  of   conversion  coating  operations   used  are
chromating,  phosphating  (either zinc  or  iron)  and complex  oxides.

A  number   of  parameters  require monitoring  and  control  to  maximize
coating formation rate and minimize the  amount  of material  discarded.

All  types of conversion  coating operations require  careful   monitoring
and control  of pH.   If the pH is not  kept  at  the optimum level,  either
the  chemical   reaction  proceeds too  slowly or the  surface of  the  coil
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 is   excessively  etched.    The  pH  of   the  system  can   be   sensed
 electronically  and  automatic make-up  of specific chemicals performed
 in  accordance with  manufacturers'  specifications.    This  control   was
 used  at   six  of  the  visited  plants.   Chemical suppliers provide  a
 series of  chemicals for  each type of conversion coating.    The   series
 includes   a   bath  make-up  and  one or   two  replenishment chemicals
 depending  upon the  constituent that  has been  depleted.    This   system
 maximizes  use  of   all   chemicals  and  provides  for a  continued  high
 quality product.

 Temperature must be constantly monitored  and kept  within an acceptable
 range.   Low   temperatures  will   slow    film   formation   and    high
 temperatures   will   degrade the freshly formed film.   For a given  coil
 speed,  there  should be adequate spray nozzle  coverage  and  pressure.
 This  assures that  all areas of the  coil  have sufficient reaction  time
 to  allow buildup of a specified film thickness.  After film formation,
 a set   of  squeegees  is   required  to  reduce  dragout   which   wastes
 unreacted  conversion coating chemicals  and contaminates  the subsequent
 sealing rinse.

 The    chromating conversion  coating  chemicals  contain  significant
 quantities of  hexavalent   and  trivalent  chromium.   The  hexavalent
 chromium   eventually becomes reduced to trivalent  chromium,  precluding
 its  use as part of  the film.   Certain  chromating   conversion coating
 systems   are   able  to   regenerate chromium.    These   systems   pump
 chromating conversion coating solution  out  of  the  process tank to
 another   tank    where   it  is  electrolytically   regenerated.    This
 application of   electrical   current   to  the  solution  increases   the
 valance of   the  trivalent  chromium  to  hexavalent chromium.    The
 solution   is   then   returned  to   the  process  tank.    This chromium
 regeneration  process  was employed  at two  plants.

 A  sealing  rinse  is used for both phosphate and  chromate conversion
 coatings.  The   sealing  rinses  are basically  dilute   solutions of
 chromic acid, phosphoric acid and  sometimes  certain metal ions such as
 zinc.   Depending  upon  the  type   of  conversion  coating  and basis
 material, various proportions of  these  constituents  are   used.    This
 sealing  rinse  removes unreacted  conversion  coating chemicals from the
 film surface, thereby  stopping  the reactions  and sealing  the effective
 pore area of  the  film  with  a layer of chromium complexes.   Similar to
 conversion  coating   operations,   the   solution  must  be  maintained at
proper  temperatures   and  spray nozzle   area  and  pressure must be
 adequate  for   the  desired  coil speed.    The  rinse  can be recirculated
 and reused until  dragged in  conversion  coating   chemicals   contaminate
 the  bath,  rinsing  action  is  affected, or  the  chemicals themselves are
depleted.   Following  the  sealing  rinse,  good  practice   provides  a
squeegee  roll  and an air  knife to  prevent dragout and to  prevent wet
strip from entering the painting operation.
                                 258

-------
The subsequent painting and baking operations are followed by a  water
spray  quench.   This  quench  cools  the basis material and films for
either subsequent coats of paint  or  final  rewinding.   The  freshly
painted  and  cured  surfaces  are  clean  and  stable and very little
contamination of the quench  water  occurs.   To  conserve  water  and
prevent  dilution  of  other  plant  wastes  discharging to treatment,
quench water can either be recycled  through  a  cooling  tower,  with
make-up water added as needed, or reused as the cleaning or conversion
coating  rinse.   Fifteen  plants  in  the data base had the necessary
equipment for partial or  full  quench  water  recycle.   Five  plants
reused a portion of their quench water as the cleaning rinse.

In-Process Substitutions

The  in-process  substitutions  for  this  industry  involve  only the
conversion coating  phases  of  the  total  operation.   The  alkaline
cleaning,  rinsing,  painting, baking, and quenching operations remain
virtually unchanged.  These inprocess substitutions  either  eliminate
the  discharge  of  a  significant  pollutant  or  entirely  eliminate
discharge from the conversion coating operation.

Certain chromating solutions contain cyanide ions  to  promote  faster
reaction  of  the  solution.   Cyanide  is  a priority pollutant which
requires separate treatment to remove it once in solution.
There are competing chemical systems that do not contain   cyanide
efforts should be made to eliminate cyanide use where possible.
and
Certain  sealing  rinses   contain   zinc  which,   is   also   a  priority
pollutant and  requires  treatment  before   being   discharged.   Efforts
should   be  made  to  incorporate   and  use  sealing  rinses  that  do  not
contain  zinc.  Several  of  the  visited  plants  used   non-zinc  sealing
rinses.

No-rinse conversion  coating   is   a  possible substitute for chromate
conversion  coating  which can   be  applied  to  steel,   galvanized  and
aluminum   basis    materials.    The   operation   eliminates  chromate
conversion  coating  bath dumps  and sealing  rinse discharges  by applying
the  coating with  a  roll coater.    Existing   lines  require extensive
modification   to  effectively use this technology.  Three plants  in  the
data base   indicated  that they  currently   use   no-rinse   conversion
coating.   The high  line speeds  and  nature of no-rinse conversion
coating  require more  precise control of cleaning,  rinsing,  and   drying
than  a  typical  conversion   coating   line   with rinsing.  No-rinse
conversion  coating  requires only   liquid   level   monitoring  as  bath
constituents  are  all  depleted  at the same  rate.
                                  259

-------
pH CONTROLLER
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-------
 10
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FIGURE VII-2. COMPARATIVE SOLUBILITIES OF METAL HYDROXIDES
             AND SULFIDE AS A FUNCTION OF pH
                                261

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-------
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                                     263

-------
                                                                   INFLUENT
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                 FIGURE VII-5. GRANULAR BED FILTRATION
                                       264

-------
 PERFORATED
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                     FIGURE V1I-6.  PRESSURE FILTRATION
                                          265

-------
SEDIMENTATION BASIN

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          FIGURE VII-7. REPRESENTATIVE TYPES OF SEDIMENTATION
                                       266

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-------
                                             FLANGE
WASTE WATER
 WASH WATER
                                                 SURFACE WASH
                                                 MANIFOLD
  BACKWASH
          INFLUENT
          DISTRIBUTOR
                                                     *- BACKWASH
                                                       REPLACEMENT CARBON
                                             CARBON REMOVAL PORT
                                                        TREATED WATER
                                                 SUPPORT PLATE
     FIGURE VII-17. ACTIVATED CARBON ADSORPTION COLUMN
                                    276

-------
CONVEYOR DRIVE
                                                          LIQUID
                                                          OUTLET
                                                                                     SLUDGE
                                                                                     INLET
  CYCLOGEAR
SLUDGE
DISCHARGE
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          RING
                            FIGURE VII-18. CENTRIFUGATION

                                                277

-------
                                      TAM£ VII-18


               TREATABILITY RATING OP PRIORITY POLLUTANTS UTILIZING CARBON ADSORPTION
 Priority Pollutant

 1.  acenaphthene
 2.  acrolein
 3.  actylonitrile
 4.  benzene
 5.  benzidine
 6.  carton tetrachlorlde
     (tetrachloromethane)
 7.  chlorobenzene
 8.  1,2,4-tricnlorobenzene
 9.  hexachlorobenzene
 10. 1,2-dichloroethane
 11. 1,1,1-trichloroethane
 12. hexachloroethane
 13. 1,1-dichloroethane
 14. 1,1,2-tcichloroethane
 15. 1,1,2,2-tetrachloiroethane
 16. chloroethane
 17. bis(chlorcmethyl)ether
 18. bis(2-chloroethyl)ether
 19. 2-chloroethyl vinyl ether
    (mixed)
 20. 2-chloronaphthalene
 21. 2,4,6-trichlorcphenol
 22. parachlorometa cresol
 23. chloroform (trichlorcmethane)
 24. 2-chlorophenol
 25. 1,2-dichlorcbenzene
 26. 1,3-dichlorobenzene
 27. 1,4-dichlorobenzene
 28. 3,3'-dichlorobenzidine
 29, 1,1-dichloroethylene
 30. 1,2-trans-dichloroethylene
 31. 2,4-dicW.orophenol
 32. 1,2-dichloropropane
 33. 1,2-dichloropropylene
    (1,3,-dicnlorcproperfc /
 34. 2,4-dinfithylpbenol
 35. 2,4-dinitrotoluene
 36. 2,6-dinitrotoiuene
 37. 1,2-diphenylhydrazine
 38. ethylbenzene
 39. fluoranthene
 40. 4-chloroFhenyl phenyl ether
 41. 4-brornophenyl phenyl ether
 42. bis(2-chloroisopropyl)ether
 43. bis(2-chloroethoxy)metharie
 44. methylene chloride
    (dichloromethane)
 45. methyl chloride (chloromethane)
 46. methyl bromide (brarcme thane)
 47. bronofonn  (t rib tenure thane)
 48. dichlorobroncnethane
Priority Pollutant
*Removal Rating          	

     H                   49.  trichlorofluoromethane        M
     L                   50.  dichlorodifluoromethane       L
     L                   51.  chlorodibroncnEthane          M
     H                   52.  hexachlorobutadiene           H
     H                   53.  hexachlorocyclopentacliene     H
     M                   54.  isophorone                    H
                         55.  naphthalene                   H
     H                   56.  nitrobenzene                  H
     H                   57.  2-nitrophenol                 H
     H                   58.  4-nitrpphenol                 H
     H                   59,  2,4-dinitrophenol             H
     H                   60.  4,6-dinitro-o-cresol          H
     H                   61.  N-nitrosodimethylamine        M
     H                   62.  N-nitrosodiphenylamine        R
     M                   63.  N-nitrosodi-n-propylamine     M
     H                   64.  pentachlorophenol             R
     L                   65.  phenol                        M
                         66.  bis(2-ethylhexyl)phthalate    H
     H                   67.  butyl benzyl phthalate        H
     L                   68.  di-n-butyi phthalate          H
                         69.  di-n-octyl phthalate          H
     R                   70.  diethyl phthalate             H
     R                   71.  dimethyl phthalate            H
     H                   72.  1,2-benzanthracene (benzo     H
     L                        (a)anthracene)
     H                   73.  benzo(a)pyrene  (3,4-tenzo-    H
     H                        pyrene)
     R                   74.  3,4-benzofluoranthene         H
     H                        (benzo(b)fluoranthene)
     H                   75.  11,12-benzofluoranthene       H
     L                        (benzo(k)fluoranthene)
     L                   76.  chrysene                      H
     H                   77,  acenaphthylene                 H
     H                   78.  anthracene                    H
     M                   79.  1,12-benzoperylene (benzo     H
                              (ghi)-perylene)
     R                   80.  fluoeene                      H
     H                   81.  phenanthrene                  H
     H                   82.  1,2,5,6-dibenzathracene       H
     R                        (dibenzo (a,h) anthracene)
     M                   83.  indeno (1,2,3-cd)  pyrene       H
     H                        (2,3-o-phenylene pyrene)
     H                   84.  pyrene
     R                   85.  tetrachloroethylene           M
     M                   86.  toluene                       H
     H                   87.  trichloroethylene              L
     L                   88.  vinyl chloride                 L
                              (chloroethylene)
     L                   106.  PCB-1242 (Arochlor 1242)       H
     L                   107.  PCB-1254 (Atochlor 1254)       H
     H                   108.  PCB-1221 (Arochlor 1221)       H
     M                   109.  PCB-1332 (Arochlor 1232)       H
                         110.  PCB-1248 {Arochlor 1248)       H
                         111.  PCB-1260 (Arochlor 1260)       H
                         112.  PCB-1016 (Arochlor 1016)       H
*Renoval Rating
*  NOTE;  Explanation of Removal RAtings

Category H (high removal)
     adsorbs at levels >_ 100 mg/g carbon at C* « 10 ing/1
     adsorbs at levels >_ 100 mg/g carbon at C£ < 1.6 ing/1

Category H (moderate renewal)
     adsorbs at levels J> 100 mg/g carbon at C- « 10 mgA
     adsorbs at levels <_100 mg/g carbon at C^ < 1.0 mg/1

Category L (low removal)
     adsorbs at levels < 100 ng/g carbon at Cf » 10 rog/l
     adsorbs at levels < 10 mg/g carbon at Cf < 1.0 mg/1

Cf - final concentrations of priority pollutant at equilibria!!
                                                  278

-------
                                TABLE VII-19
               CLASSES OF ORGANIC COMPOUNDS ADSORBED ON CARBON
Organic Chemical Class

Aromatic Hydrocarbons

Polynuclear Aromatics


Chlorinated Aromatics



Phenolics


Chlorinated Phenolics
High Molecular Weight Aliphatic and
Branch Chain Hydrocarbons

Chlorinated Aliphatic Hydrocarbons
High Molecular Weight Aliphatic Acids
and Aromatic Acids

High Molecular Weight Aliphatic Amines
and Aromatic Amines

High Molecular Weight Ketones, Esters,
Ethers and Alcohols

Surfactants

Soluble Organic Dyes
Examples of Chemical Class

benzene, toluene, xylene

naphthalene, anthracene
bephenyls

chlorobenzene, polychlorinated
biphenyls, aldrin, endrin,
toxaphene, DDT

phenol, cresol, resorcenol
and polyphenyls

trichlorophenol, pentachloro-
phenol

gasoline, kerosine
carbon tetrachloride,
perchloroethylene

tar acids, benzoic acid
aniline, toluene diamine


hydroquinone, polyethylene
glycol

alkyl benzene sulfonates

melkylene blue, Indigo carmine
High Molecular Weight includes compounds in the broad range of from 4 to 20
carbon atoms.
                                      279

-------
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-------
    CONTROLS
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TANK
                                       TREATED
                                        WASTE
      RAW WASTE-
FIGURE VII-20. TYPICAL OZONE PLANT FOR WASTE TREATMENT
                            281

-------
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                 FIGURE VII-21.  UV/OZONATION
                                  282

-------
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-------
OILY WATER
INFLUENT
                         MOTOR
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                                                                          EXCESS
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                                                                          LEVEL
                                                                          CONTROLLER
                     FIGURE VII-23. DISSOLVED AIR FLOTATION
                                              284

-------
   CONDUIT
   TO MOTOR
INFLUENT
 CONDUIT TO
 OVERLOAD
 ALARM
                                                  COUNTERFLOW
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                                   DIRECTION OF ROTATION
     EFFLUENT PIPE
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 INFLUENT 	»
CENTER COLUMN
  CENTER CAGE
                                                                          WEIR
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                    CENTER SCRAPER
                                                                        SQUEEGEE
                       FIGURE VII-24. GRAVITY THICKENING

                                              285

-------
WASTE WATER CONTAINING
DISSOLVED METALS OR
OTHER IONS
                                                    DIVERTER VALVE
                                                          DISTRIBUTOR
       REGENERANT
       SOLUTION
                                                         SUPPORT
    REGENERANT TO REUSE,
    TREATMENT, OR DISPOSAL
                                                   -DIVERTER VALVE
METAL-FREE WATER
FOR REUSE OR DISCHARGE
               FIGURE VII-25.  ION EXCHANGE WITH REGENERATION
                                            286

-------
                                            MACROMOLECULES
                                            AND SOLIDS
MEMBRANE
                                                                          = 450 PSI
             PERMEATE (WATER)
     FEED
             O  SALTS OR SOLIDS

             •  WATER MOLECULES
                                           WATER
                                                     MEMBRANE CROSS SECTION,
                                                     INI TUBULAR, HOLLOW FIBER,
                                                     OR SPIRAL-WOUND CONFIGURATION
CONCENTRATE
  (SALTS)
              FIGURE V1I-26.  SIMPLIFIED REVERSE O>SMOSIS SCHEMATIC
                                               287

-------
                                PERMEATE
                                TUBE
                                  ADHESIVE BOUND

                                           SPIRAL MODULE
         PERMEATE
                   FLOW
                       FEED
                                                                    CONCENTRATE
                                                                    FLOW
                                                          BACKING MATERIAL
                                               •MESH SPACER
                                        •MEMBRANE
                                   SPIRAL MEMBRANE MODULE
              POROUS SUPPORT TUBE
              WITH MEMBRANE
                    BRACKISH
                    WATER
                    FEED FLOW
                       PRODUCT WATER
                       PERMEATE FLOW
                                                                         BRINE
                                                                         CONCENTRATE
                                                                         FLOW
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   SNAP
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SEAL
                                                           OPEN ENDS
                                                           OF FIBERS
                                                               EPOXY
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POROUS
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OUTLET
   END PLATE
                                             POROUS FEED
                                             DISTRIBUTOR TUBE	'
                                                                                      PERMEATE
                                                                     END PLATE
                                   HOLLOW FIBER MODULE

             FIGURE VII-27. REVERSE OSMOSIS MEMBRANE CONFIGURATIONS
                                                  288

-------










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                    FIGURE Vll-28.  SLUDGE DRYING BED
                                          289

-------
  ULTRAFILTRATION
                                 MACROMOLECULES
 P- 10-50 PSI
MEMBRANE
                                       WATER       SALTS
                                                 -MEMBRANE
              PERMEATE

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    FIGURE VII-29. SIMPLIFIED ULTRAFILTRATION FLOW SCHEMATIC
                                        290

-------
            FABRIC OR WIRE
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            STRETCHED OVER
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SOLIDS SCRAPED
OFF FILTER MEDIA
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                                       TO BE
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                            FIGURE VII-30.  VACUUM FILTRATION
                                                      291

-------

-------
                             SECTION VIII

              COST OF WASTE WATER CONTROL AND TREATMENT
INTRODUCTION

This   section   presents  estimates  of  the  costs  of  implementing
wastewater treatment and control options for each of the subcategories
included in the Coil Coating Category.  These cost estimates, together
with the estimated pollutant reduction performance for each  treatment
and  control option presented in Sections IX, X, XI, and XII provide a
basis for evaluating the options presented and identification  of  the
best  practicable  control  technology currently available (BPT), best
available technology economically achievable (BAT), best  demonstrated
technology (BDT), and the best alternative for pretreatment.  The cost
estimates  also  provide  the  basis  for the determining the probable
economic  impact  on  the  coil  coating  category  of  regulation  at
different  pollutant  discharge  levels.   In  addition,  this section
addresses  non-water  quality  environmental  impacts  of   wastewater
treatment  and  control  alternatives,  including air pollution, noise
pollution, solid wastes, and energy requirements.

In developing the  cost  estimates  presented  in  this  section,  EPA
selected  specific  wastewater  treatment  technologies and  in-process
control techniques from among  those  discussed  in  Section  VII  and
combined  them in wastewater treatment and control systems appropriate
for each subcategory.  As described in more detail  below,   investment
and  annual  costs  for each system were estimated based on wastewater
flow rates and raw  waste  characteristics  for  each  subcategory  as
presented  in  Section  V.   Cost  estimates  are  also  presented for
individual treatment technologies  included  in  the  waste  treatment
systems.

COST ESTIMATION METHODOLOGY             ,

Cost estimation is accomplished using a computer program which accepts
inputs  specifying  the  treatment  system  to  be estimated, chemical
characteristics of the raw  waste  streams  treated,  flow   rates  and
operating   schedules.   The  program  accesses  models  for  specific
treatment components which relate component  investment  and  operating
costs,   materials   and  energy  requirements,  and  effluent   stream
characteristics to influent flow  rates  and  stream  characteristics.
Component  models  are  exercised  sequentially  as the components are
encountered in the system to determine  chemical   characteristics  and
flow  rates  at each point.  Component  investment  and annual costs are
also determined and used  in the computation  of  total  system   costs.
Mass balance calculations are used to determine the characteristics of
combined  streams  resulting  from  mixing   two or more streams  and to
                                  293

-------
determine the volume  of  sludges  or  liquid  wastes  resulting  from
treatment operations such as sedimentation, filtration, flotation, and
oil separation.

Cost  estimates  are  broken  down  into  several distinct elements in
addition  to  total  investment  and  annual  costs:   operation   and
maintenance  costs,  energy  costs,  depreciation, and annual costs of
capital.  The cost  estimation  program  incorporates  provisions  for
adjustment  of  all  costs  to  a  common  dollar base on the basis of
economic  indices  appropriate  to  capital  equipment  and  operating
supplies.   Labor  and  electrical  power  costs  are  input variables
appropriate to the dollar base year for cost  estimates.   These  cost
breakdown  and adjustment factors as well as other aspects of the cost
estimation process are discussed in greater detail  in  the  following
paragraphs.

Cost Estimation Input Data

The  waste  treatment  system  descriptions input to the computer cost
estimation program include both a specification of the waste treatment
components included and a definition of their  interconnections.   For
some  components,  retention  times  or other operating parameters are
specified in the input, while for others, such as  reagent  mix  tanks
and  clarifiers,  these  parameters  are  specified within the program
based on prevailing design practice  in  industrial  waste  treatment.
The waste treatment system descriptions may include multiple raw waste
stream  inputs  and  multiple  treatment trains.  For example, Cyanide
bearing waste streams are segregated and treated for cyanide oxidation
prior to mixing with other chromium bearing wastes  for  chromium  re-
duction  and  subsequent  chemical  precipitation  treatment  with the
remaining process wastewater.

The specific treatment systems selected for cost estimation  for  each
subcategory were based on an examination of raw waste characteristics,
consideration   of  manufacturing  processes,  and  an  evaluation  of
available  treatment  technologies  discussed  in  Section   V.    The
rationale  for  selection of these systems is presented in Section IX,
which also discusses their pollution removal effectiveness.

The input data set also includes chemical characteristics for each raw
waste stream (specified as input to the treatment  systems  for  which
costs  are  to  be estimated).  These characteristics are derived from
the raw waste sampling data presented in  Section  V.   The  pollutant
parameters   which  are  presently  accepted  as  input  by  the  cost
estimation program appear in Table VIII-1 (page 321).  The  values  of
these parameters are used in determining materials consumption, sludge
volumes,  treatment component sizes and effluent characteristics.  The
list of  input  parameters  is  expanded  periodically  as  additional
pollutants   are  found  to  be  significant  in  waste  streams  from
                                 294

-------
industries under study and as additional treatment technology cost and
performance data become available.  For  the  coil  coating  category,
individual  subcategories  commonly  encompass  a  number of different
waste streams which  are  present  to  varying  degrees  at  different
facilities.   The  raw  waste  characteristics shown as  input to waste
treatment represent a mix of these streams including  all  significant
pollutants   generated  in  the  subcategory  and  do  not  correspond
precisely to process wastewater at any existing facility.  The process
by which these raw wastes were defined is explained in Section V.

The final input data set comprises raw waste flow rates  for each input
stream for one or more plants in each  subcategory  addressed.   Three
cases  corresponding  to  high,  low  and typical flows  encountered at
existing facilities were used for each  coil  coating  subcategory  to
represent  the range of treatment costs which would be incurred in the
implementation of each  control  and  treatment  option  offered.   In
addition,  data corresponding to the flow rates reported by each plant
in the category were input to the computer to provide  cost  estimates
for use in economic impact analysis.

System Cost Computation

Figure  VIII-1  (page  322)  presents  a simplified flow chart for the
estimation of wastewater treatment and control costs  from  the  input
data  described  above.  In the computation, raw waste characteristics
and flow rates for the first case are used as input to the  model  for
the  first  treatment  technology  specified in the system definition.
This model is used to determine the size and cost  of  the  component,
materials  and  energy  consumed  in its operation, and  the volume and
characteristics of the stream(s) discharged  from  it.   These  stream
characteristics  are  then  used  as  input  to  the next component(s)
encountered in the system definition.   This  procedure  is  continued
until  the complete system costs and the volume and characteristics of
the final effluent stream(s) and sludge  or  concentrated  oil  wastes
have been determined.  In addition to treatment components, the system
may include mixers in which two streams are combined, and splitters in
which  part  of  a  stream  is directed to another destination.  These
elements are handled by  mass  balance  calculations  and  allow  cost
estimation for specific treatment of segregated process  wastes such as
oxidation  of  cyanide  bearing wastes prior to combination with other
process wastes for further treatment, and  representation  of  partial
recycle of wastewater.

As   an   example   of  this  computation  process,  the  sequence  of
calculations involved in the development of  cost  estimates  for  the
simple  treatment  system  shown  in  Figure  VIII-2 (page 323) may be
described.  Initially,  input specifications for the  treatment  system
are  read  to  set  up  the  sequence of computations.   The subroutine
addressing chemical precipitation and clarification is then  accessed.
                                 295

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The  sizes  of  the mixing tank and clarification basin are calculated
based on the raw waste flow rate to provide 45 minute retention in the
mix tank and 4 hour retention with 33.3 gph/ft2 surface loading in the
clarifier.  Based on these sizes,  investment  and  annual  costs  for
labor,  supplies  for  the mixing tank and clarifier including mixers,
clarifier rakes and other directly related equipment  are  determined.
Fixed  investment  costs  are  then added to account for sludge pumps,
controls and reagent feed systems.

Based on the input  raw  waste  concentrations  and  flow  rates,  the
reagent  additions (lime, alum, and polyelectrolyte) are calculated to
provide fixed concentrations  of  alum  and  polyelectrolyte  and  10%
excess  lime  over  that required for stoichiometric reaction with the
acidity and metals present in the waste stream.  Costs are  calculated
for  these  materials,  and  the suspended solids and flow leaving the
mixing tank and entering the clarifier are increased  to  reflect  the
lime  solids  added  and  precipitates  formed.  These modified stream
characteristics are then used  with  performance  algorithms  for  the
clarifier (as discussed in Section VII) to determine concentrations of
each pollutant in the clarifier effluent stream.  By mass balance, the
amount  of  each  pollutant in the clarifier sludge may be determined.
The volume of the sludge stream is determined by the concentration  of
TSS,  which  is  fixed  at 4-5% based on general operating experience;
concentrations of other pollutants in the sludge stream are determined
from their masses and the volume of the stream.

The subroutine describing vacuum filtration  is then  called,  and  the
mass  of  suspended  solids  in the clarifier sludge stream is used to
determine the size and investment cost of the vacuum filtration  unit.
Operating  hours  for the filter are calculated from the flow rate and
TSS concentration and are used  to  determine  manhours  required  for
operation.   Maintenance  labor  requirements  are  added  as  a fixed
additional cost.

The sludge flow rate and TSS content are then used to determine  costs
of  materials  and supplies for vacuum filter operation  including  iron
and alum  added as filter aids, and  the  electrical  power  costs  for
operation.  Finally, the vacuum filter performance algorithms are  used
to  determine  the  volume  and  characteristics  of the vacuum filter
sludge and filtrate, and the costs of contract disposal of the  sludge
are calculated.  The recycle of vacuum filter filtrate to the chemical
precipitation-clarification    system   is    not   reflected   in   the
calculations due to the difficulty of iterative solution of such loops
and the general observation that the contributions of such streams  to
the total flow and pollutant levels are  in practice, negligibly small.
Such  minor contributions are  accounted  for  in the 20% excess capacity
provided  in most components.
                                  296

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The costs determined for all components of the system are  summed  and
subsidiary   costs  are  added  to  provide  output  specifying  total
investment and annual costs  for  the  system  and  annual  costs  for
capital,  depreciation,  operation and maintenance, and energy.  Costs
for specific system components and the characteristics of all  streams
in the system may also be specified as output from the program.

Treatment Component Models               j

The   cost   estimation  program  presently  incorporates  subroutines
providing  cost  and  performance  calculations  for   the   treatment
technologies  identified  in Section VII.  These subroutines have been
developed over a period of years from the best available  information,
including  on-site observations of treatment system performance, costs
and construction practices at a large number of industrial facilities,
published data, and information obtained from suppliers of  wastewater
treatment equipment.  The subroutines are modified and new subroutines
added  as improvements in treatment technologies become available, and
as additional treatment technologies are required for  the  industrial
wastewater  streams  under  study.  Specific discussion of each of the
treatment component models used in costing  wastewater  treatment  and
control  systems  for  the coil coating category is presented  later in
this section where cost estimation is addressed, and  in  Section  VII
where performance aspects were developed,,

In   general  terms,  cost  estimation  is  provided  by  mathematical
relationships in each subroutine approximating  observed  correlations
between   component   costs   and  the  most  significant  operational
parameters such as water flow rate,  retention  times,  and  pollutant
concentrations.   In  general, flow rate is the primary determinant of
investment costs and of  most  annual  costs  with  the  exception  of
materials  costs.  In some cases, however, as discussed for the vacuum
filter, pollutant  concentrations  may  also  significantly  influence
costs.

Cost Factors and Adjustments

As  previously  indicated,  costs are adjusted to a common dollar base
and are generally influenced by a number of factors including: Cost of
Labor, Cost of Energy, Capital Recovery Costs and  Debt-Equity  Ratio.
These cost adjustments and factors are discussed below.

Dollar Base - A dollar base of January 1978 was used for all costs.

Investment  Cost  Adjustment  -  Investment costs were adjusted to the
aforementioned dollar base  by  use  of  the  Sewage  Treatment  Plant
Construction  Cost  Index.   This cost is published monthly by the EPA
Division of  Facilities  Construction  and  Operation.   The   national
average of the Construction Cost Index for January 1978 was 288.0.
                                 297

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Supply  Cost  Adjustment - Supply costs such as chemicals were related
to the dollar base by the Wholesale  Price  Index.   This  figure  was
obtained   from   the  U.S.  Department  of  Labor,  Bureau  of  Labor
Statistics, "Monthly Labor Review".  For January 1978 the  "Industrial
Commodities"  Wholesale  Price  Index  was  201.6.  Process supply and
replacement costs were included in the estimate of the  total  process
operating and maintenance cost.

Cost  of  Labor - To relate the operating and maintenance labor costs,
the hourly wage rate for non-supervisory workers in water, stream, and
sanitary systems was used from the U.S. Department of Labor, Bureau of
Labor Statistics Monthly publication, "Employment and Earnings".   For
January  1978,  this wage rate was $6.00 per hour.  This wage rate was
then applied to  estimates  of  operation  and  maintenance  man-hours
within  each  process  to obtain direct labor charges.  To account for
indirect labor charges, 10 percent of the direct labor costs was added
to the direct labor charge to yield estimated total labor costs.  Such
items  as  Social  Security,  employer  contributions  to  pension  or
retirement  funds,  and  employer-paid  premiums  to  various forms of
insurance programs were considered indirect labor costs.

Cost of Energy - Energy requirements were calculated  directly  within
each  process.   Estimated  costs  were then determined by applying an
electrical rate of 3.3 cents per kilowatt hour.

The electrical  charge  for  January  1978  was  corroborated  through
consultation  with  the  Energy  Consulting Services Department of the
Connecticut Light and  Power  Company.   This  electrical  charge  was
determined  by assuming that any electrical needs of a waste treatment
facility or in-process technology would be satisfied  by  an  existing
electrical  distribution system; i.e., no new meter would be required.
This eliminated the formation of any new  demand  load  base  for  the
electrical charge.

Capital  Recovery  Costs  -  Capital  recovery costs were divided into
straight line ten-year depreciation and  cost  of  capital  at  a  ten
percent  annual interest rate for a period of ten years.  The ten year
depreciation  period  was  consistent  with   the   faster   write-off
(financial  life)  allowed  for  these  facilities,  even  though  the
equipment life is in the range of 20 to 25 years.  The annual cost  of
capital was calculated by using the capital recovery factor approach.

The  capital  recovery  factor  is  normally  used in industry to help
allocate  the  initial  investment  and  the  interest  to  the  total
operating cost of the facility.  It is equal to:

                         CRF = i +    i
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where  i is the annual interest rate and N is the number of years over
which the capital is to be recovered.  The annual capital recovery was
obtained by multiplying the initial investment by the capital recovery
factor.   The  annual  depreciation  of  the  capital  investment  was
calculated  by  dividing  the  initial  investment by the depreciation
period N, which was assumed to be  ten  years.   The  annual  cost  of
capital  was  then  equal  to  the  annuial  capital recovery minus the
depreciation.                           i

Debt-Equity Ratio - Limitations on new borrowings assume that debt may
not exceed a set percentage of the shareholders equity.  This  defines
the  breakdown  of  the  capital  investment  between  debt and equity
charges.  However, due to the lack of information about the  financial
status  of  various  plants,  it  was not feasible to estimate typical
shareholders equity to obtain debt financing  limitations.   For  these
reasons,  no attempt was made to break down the capital cost into debt
and equity charges.  Rather, the annual cost  of capital was calculated
via the procedure outlined  in  the  Capital  Recovery  Costs  section
above.

Subsidiary Costs                        |

The waste treatment and control system costs  presented in Tables VIII-
19  through VII1-42 for end-of-pipe and in-process waste water control
and treatment systems include subsidiary costs associated with  system
construction and operation.  These subsidiary costs include:

          administration and laboratory facilities

          garage and shop facilities

          line segregation

          yardwork

          land
          engineering

          legal,  fiscal,  and
administrative
           interest  during  construction

 Administrative  and  laboratory  facility   treatment   investment   is   the
 cost  of  constructing  space for administration,  laboratory,  and service
 functions   for   the  waste  water   treatment   system.    For these  cost
 computations,  it was   assumed   that  there  was already  an  existing
 building   and   space  for  administration,   laboratory,   and   service
 functions.   Therefore,  there was no investment cost for  this item.
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For laboratory operations, an analytical  fee  of  $90   (January  1978
dollars) was charged for each wastewater sample, regardless of whether
the  laboratory  work was done on or off site.  This analytical fee is
typical of the charges experienced by  Hamilton  Standard  during  the
past several years of sampling programs.  The frequency of waste water
sampling  is a function of waste water discharge flow and is presented
in Table VIII-2  (page 324).  This frequency was suggested by the Water
Compliance Division of the USEPA.

Industrial waste treatment facilities were assumed to need  no  garage
and  shop  investment because this cost item was assumed to be part of
the normal plant costs.

Line segregation investment costs account for plant  modifications  to
segregate  wastes.  The investment costs for line segregation included
placing a trench in the existing plant floor and installing the  lines
in  this trench.  The same trench was used for all pipes and a gravity
feed to the treatment system was assumed.  The pipe was assumed to run
from the center of the floor to a corner.  A rate of 2.04  liters  per
hour  of  waste water discharge per square meter of area (0.05 gallons
per hour per square foot) was  used  to  determine  floor  and  trench
dimensions from waste water flow rates for use in this cost estimation
process.

The  yardwork  investment  cost item includes the cost of general site
clearing, intercomponent  piping,  valves,  overhead  and  underground
electrical  wiring,  cable,  lighting,  control  structures, manholes,
tunnels, conduits, and  general  site  items  outside  the  structural
confines  of  particular  individual  plant  components.  This cost is
typically 9 to 18  percent  of  the  installed  components  investment
costs.   These cost estimates, were based on an average of 14 percent.
Annual yardwork operation and maintenance costs are considered a  part
of  normal  plant  maintenance  and  were  not  included in these cost
estimates.

No new land purchases were required.  It was  assumed  that  the  land
required for the end-of-pipe treatment system was already available at
the plant.

Engineering  costs  include  both  basic  and special services.  Basic
services include preliminary  design  reports,  detailed  design,  and
certain  office  and field engineering services during construction of
projects.  Special  services  include  improvement  studies,  resident
engineering,   soils   investigations,  land  surveys,  operation  and
maintenance manuals, and other  miscellaneous  services.   Engineering
cost  is a function of process installed and yardwork investment costs
and ranges between 5.7 and 14% depending on the total of these costs.
                                 300

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Legal, fiscal and administrative costs  relate  to  the  planning  and
construction  of  waste  water  treatment  facilities and include such
items as preparation of legal documents, preparation  of  construction
contracts,  acquisition  to  land, etc.  These costs are a function of
process installed, yardwork, engineering, and  land  investment  costs
ranging between 1 and 3 percent of the total of these costs.

Interest  cost  during  construction  is  the interest cost accrued on
funds from the time payment is made to the contractor to  the  end  of
the  construction  period.   The total of all other project investment
costs (process installed;  yardwork;  land;  engineering;  and  legal,
fiscal, and administrative) and the applied interest affect this cost.
An interest rate of 10 percent was used to determine the interest cost
for  these  estimates.   In general, interest cost during construction
varies between 3 and 10% of total system costs depending on the  total
costs.

COST ESTIMATES FOR INDIVIDUAL TREATMENT TECHNOLOGIES

Introduction

Treatment technologies have been selected from among the larger set ot
available  alternatives  discussed  in  Section VII on the basis o£ ah
evaluation of raw waste characteristics, typical plant characteristics
(e.g.  location,  production  schedules,   product   mix,   and   larid
availability),    and   present   treatment   practices   within   the
subcategories  addressed.   Specific  rationale   for   selection   is
addressed  in  Sections  IX,  X,  XI and XII.  Cost estimates for each
technology addressed in this  section   include  investment  costs  ahd
annual costs for depreciation, capital, operation and maintenance, and
energy.

Investment  -  Investment  is the capital expenditure required to bring
the technology into operation.   If  the  installation  is  a  package
contract,  the  investment  is  the  purchase  price  of the installed
equipment.   Otherwise,  it  includes   the  equipment  cost,  cost  of
freight,  insurance and taxes, and installation costs.
Total  Annual
Cost - Total annual cost is the sum of annual costs for
                                   (less
depreciation, capital, operation and maintenance
energy  (as a separate function).
energy),   and
Depreciation - Depreciation  is an allowance,  based  on  tax  regulations,
for  the recovery of fixed capital from an  investment  to be  considered
as a non-cash annual expense.  It may  be  regarded as   the  decline   in
value of a capital asset due to wearout and obsolescence.

Capital  -  The  annual  cost of capital  is the  cost,  to the plant,  of
obtaining capital expressed  as an interest  rate.  It  is equal  to   the
                                  301

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capital  recovery
depreciation.
cost (as previously discussed on cost factors) less
Operation and Maintenance - Operation  and  maintenance  cost  is  the
annual  cost  of  running  the  waste  water  treatment equipment.  It
includes labor and materials such as waste  treatment  chemicals.   As
presented  on  the  tables,  operation  and  maintenance cost does not
include energy (power or fuel) costs because  these  costs  are  shown
separately.

Energy - The annual cost of energy is shown separately, although it is
commonly  included  as part of operation and maintenance cost.  Energy
cost has been shown  separately  because  of  its  importance  to  the
nation's economy and natural resources.

Cyanide Oxidation

In  this  technology,  cyanide  is  destroyed  by reaction with sodium
hypochlorite under alkaline conditions.  A complete  system  for  this
operation  includes  reactors, sensors, controls, mixers, and chemical
feed  equipment.   Control  of  both  pH  and  chlorine  concentration
(through  oxidation-reduction  potential)  is  important for effective
treatment.

Capital Costs.  Capital costs for cyanide oxidation  shown  in  Figure
VIII-3  (page  325)  include  reaction tanks, reagent storage, mixers,
sensors and controls necessary for operation.  Costs are estimated for
both batch and continuous systems with the operating mode selected  on
a least cost basis.   Specific costing assumptions are as follows:

For both continuous and batch treatment, the cyanide oxidation tank is
sized  as  an above ground cylindrical tank with a retention time of  4
hours based on the process flow.  Cyanide oxidation is  normally  done
on  a  batch  basis;  therefore,  two  identical  tanks  are employed.
Cyanide is removed by the addition of sodium hypochlorite with  sodium
hydroxide  added  to maintain the proper pH level.  A 60-day supply of
sodium hypochlorite is stored in an  in-ground covered  concrete  tank,
0.3  m  (1  ft)  thick.   A  90-day  supply of sodium hydroxide also is
stored in an in-ground covered concrete tank, 0.3 m (1 ft) thick.

Mixer power requirements for both continuous and batch  treatment  are
based  on  2  horsepower  for  every  11,355 liters  (3,000 gal) of tank
volume.  The mixer is assumed to be  operational  25 percent of the time
that the treatment system  is operating.
A continuous  control  system  is  costed
alternative.   This  system  includes:
                     for   the   continuous   treatment
           immersion  pH  probes  and  transmitters
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     2    immersion ORP probes and transmitters
     2    pH and ORP monitors
     2    2-pen recorders               i
     2    slow process controller
     2    proportional sodium hypochlorite pumps
     2    proportional sodium hydroxide pumps
     2    mixers
     3    transfer pumps
     1    maintenance kit
     2    liquid level controllers and alarms, and miscellaneous
          electrical equipment and piping
A  complete
alternative.
   manual  control  system is costed for the batch treatment
    This system includes:
     2
     1
     1
     1
     1
pH probes and nonitors
mixer                         j
liquid level controller and horn
proportional sodium hypochlorite pump
on-off sodium hydroxide pump and PVC piping from the
chemical storage tanks
Operation and Maintenance Cost.  Operation and maintenance  costs  for
cyanide  oxidation  include labor requirements to operate and maintain
the system;  electric  power  for  mixers,  pumps  and  controls,  and
treatment chemicals.  Labor requirements for operation and maintenance
are shown in Figure VIII-4 (page 326).  As can be seen operating labor
is  substantially  higher  for  batch  treatment  than  for continuous
operation.  Maintenance labor requirements  for  continuous  treatment
are fixed at 150 manhours per year for flow rates below 23,000 gph and
thereafter increase according to:

     Labor = .00273 x (Flow-23000) + 150
Maintenance
negligible.
   labor  requirements for batch treatment are assumed to be
Annual  costs  for  treatment  chemicals  and  electrical  power   are
presented  in  Figure  VIII-5  (page  327).   Chemical  additions  are
determined from cyanide, acidity, and flow  rates  of  the  raw  waste
stream according to:

     Ibs sodium hypochlorite = 62.96 x Ibs CN-
     Ibs sodium hydroxide = 0.8 x Ibs acidity

Chromium Reduction

This  technology  chemically  reduces  hexavalent  chromium under acid
conditions to allow  subsequent  removal  of  the  trivalent  form  by
                                 303

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precipitation  as  the hydroxide.  Treatment may be provided in either
continuous or batch mode, and cost estimates are developed  for  both.
Operating  mode  .for system cost estimates is selected on a least cost
basis.

Capital cost.  Cost  estimates   include  all  required  equipment  for
performing   this  treatment  technology,  including  reagent  dosage,
reaction tanks, mixers and controls.  Different reagents are  provided
for  batch  and  continuous  treatment  resulting  in different system
design considerations as discussed below.

For both continuous and batch treatment, sulfuric acid is added for pH
control.  A 90 day supply is stored in the 25 percent aqueous form  in
an above-ground, covered concrete tank, 0.305 m 91 ft) thick.

For  continuous chromium reduction, the single chromium reduction tank
is sized in an above-ground cylindrical concrete tank with a  0.305  m
(1  ft)  wall  thickness,  a  45  minute retention time, and an excess
capacity factor of 1.2.   Sulfur  dioxide  is  added  to  convert  the
influent hexavalent chromium to  the trivalent form.

The control system for continuous chromium reduction consists of:

     1    immersion pH probe and transmitter
     1    immersion ORP probe and transmitter
     1    pH and ORP monitor
     2    slow process controllers
     1    sulfonator and associated pressure regulator
     1    sulfuric acid pump
     1    transfer pump for sulfur dioxide ejector
     2    maintenance kits for electrodes, and miscellaneous
          electrical equipment and piping

For  batch  chromium  reduction, the dual chromium reduction tanks are
sized as above-ground cylindrical  concrete  tanks,  0.305  m   (1  ft)
thick,  with a 4 hour retention  time, and an excess capacity factor of
1.2.  Sodium bisulfite is added  to reduce the hexavalent chromium.
A completely manual system  is
sidiary equipment  includes:
provided  for  batch  operation.   Sub-
      1    sodium bisufite mixing and  feed  tank
      1    metal stand and agitator  collector
      1    sodium bisulfite mixer with disconnects
      1    sulfuric acid pump
      1    sulfuric acid mixer with  disconnects
      2    immersion pH probes
      1    pH monitor, and miscellaneous piping
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Capital costs for batch and continuous treatment systems are presented
in Figure VIII-6 (page 328).            ,

Operation  and  Maintenance.   Costs  for  operating  and  maintaining
chromium reduction  systems  include  labor,  chemical  addition,  and
energy requirements.  These factors are determined as follows:

     LABOR
                                        i
The labor requirements are  plotted  in  Figure  VIII-7  (page  3293).
Maintenance  of the batch system is assumed to be negligible and so it
is not shown.

     CHEMICAL ADDITION                  !
                                        i
For the continuous sytem, sulfur dioxide is  added  according  to  the
following:                              i

     (Ibs SO2/day) =  (15.43) (flow to unit-MGD)  (Cr+6 mg/1)

In  the  batch  mode,  sodium  bisulfite  is  added in place of- sulfur
dioxide according to  the following:

     (Ibs NaHS03/day) =  (20.06)  (flow to unit-MGD) (Cr+6 mg/1)

     ENERGY

Two horsepower  is  required  for  chemical  mixing.   The  mixers  are
assumed  to  operate  continuously  over  the  operation   time  of the
treatment system.

Given  the above requirements,  operation  and  maintenance costs  are
calculated based on the  following:

          $6.00 per man  +  10%  indirect  labor charge
          $380/ton of sulfur dioxide    i
          $20/ton of  sodium bisulfite   ,
          $0.032/kilowatt  hour of required  electricity

Oil Skimming

This   technology  removes   oils  from   process   wastewater by gravity
separation and  subsequent  removal of the  surface  layer   of  oil.    A
baffled  tank provides quiescent conditions conducive to separation of
oil droplets and retention of  floating  oil  behind  an underflow baffle.

Capital Cost.   The  costing analyses for the API  Oil  Skimming  process
were   based  upon   an optimization  of the one channel oil  separator
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design  by  expanding  the  API  design  standards.
assumptions were used for costing purposes:
              The   following
1.    The unit was assumed to be an  in-the-ground  rectangular  cross-
     section  concrete  tank with a maximum horizontal stream velocity
     set to the smaller of 3 fpm or 4.72 times the oil rise rate.

2.    The  depth-to-width  ratio  was  maintained  between  0.3-0.5  to
     minimize tank size.

3.    The depth  was  maintained  between  3  ft.  minimum  and  8  ft.
     maximum,  and the width between 6 ft. minimum and 20 ft.  maximum
     to provide minimum tank size.
4.    The costs were based on a 0.3 m {1
     include the excavation required.
ft)  concrete  thickness  and
Figure  VIII-8  (page  330)  presents  estimated oil separator capital
costs.  Flows up to 0.25 MGD are  costed  for  a  single  unit;  flows
greater than 0.25 MGD, require more than one unit.

Operation  and  Maintenance  Cost.   Only  labor  is  included  in the
operation and maintenance costs of the skimmer since other costs  were
considered  negligible  in comparison.  Figure VIII-9 (page 331) illu-
strates the correlation used to calculate the required  man-hours  for
operation and maintenance.  The total man-hours are then multiplied by
the $6.00 per hour labor rate plus 10% indirect labor charge.

Chemical Precipitation and Clarification

This  technology  removes dissolved pollutants by first reacting added
lime and sodium sulfide to form precipitates  and  then  removing  the
precipitated  solids  by  gravity  settling  in  a clarifier.  Several
distinct operating modes and construction  techniques  are  costed  to
provide  least  cost  treatment  over  a  broad  range  of flow rates.
Because  of  their  interrelationships  and  integration   in   common
equipment in some installations, both the chemical addition and solids
removal equipment are addressed in a single subroutine.

Investment  Cost.  Investment costs are determined for this technology
for continuous treatment systems using either steel tank  or  concrete
construction,  and  for  batch  treatment.   The  least cost system is
selected for each application.  Continuous treatment systems include a
mix tank for reagent feed addition  and  a  clarification  basin  with
associated  sludge  rakes  and  pumps.   Batch treatment includes only
reaction-settling tanks and sludge pumps.

For the continuous treatment systems, construction  is  different  for
flows  above  and  below  2604  gph.   For flow rates to the clarifier
                                 306

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greater than or  equal  to  2604  gallons  per  hour,  the  continuous
treatment  clarifier  costs  include a flocculator, settling tank, and
associated  equipment.   For  flow  rates  less  than  2604  gph,  the
continuous  clarifier  costs include two above-ground tanks instead of
the in-ground flocculator-settling tank combination.

The in-ground flocculator is a concrete unit.  The size is based on  a
45  minute  retention time, a length to width ratio of 5, a depth of 8
feet, a wall thickness of 1 foot, and a 20  percent  excess  capacity.
Capital   costs   include  excavation  and  a  mixer.   The  estimated
flocculator cost is shown in Figure VIII-10  (page 332).

The in-ground settling tank is a concrete unit sized for  a  hydraulic
loading  of  33.3  gph/square  foot,  a  4 hour retention time, and an
excess capacity of 20 percent.  Capital costs include excavation and a
skimmer.  Figure VIII-11 (page 333) shows  the  combined  flocculator-
settling tank cost for flows greater tha.n 2604 gallons per hour.

The  two above-ground conical unlined cairbon steel tanks are sized for
four hour retention in each tank.  Figure VIII-11 shows the  cost  for
these tanks for flows less than 2604 gph.

A  cost  of  $3202 is included in clarifier  capital cost estimates for
sludge pumps regardless of whether the dual  above-ground tanks or  the
in-ground  flocculator-settling  tank combination are used.  This cost
covers the expense for two centrifugal sludge pumps.

For batch treatment, dual above-ground cylindrical carbon steel  tanks
sized  for  8  hour retention and 20 percent excess capacity are used.
If the required tank volume exceeds 50,000   gallons,  then  costs  for
field fabrication are included.  The capital cost for the batch system
(not including the sludge pump costs) is shown in Figure VIII-12  (page
334).   The  capital cost estimate for batch treatment also includes a
fixed $3,202 cost for sludge pumps as discussed above.

Figure VII1-13 (page 335) shows  a  comparison  of  the  capital  cost
curves  for  the  modes  discussed above.  These curves  include sludge
pump cost contributions.

All costs include motors, starters, alt€?rnators, and necessary piping.

OPERATION AND MAINTENANCE COSTS         i

The operation and maintenance costs for the  clarifier routine  include:

     1)   Cost of chemicals added  (lime,, sodium sulfide)
     2)   Labor  (operation and maintenance)
     3)   Energy
                                  307

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Each of these contributing factors are discussed below.

     CHEMICAL COST

     Lime and sodium sulfide are added for metals .and solids  removal.
     The amount of chemical required is based on equivalent amounts of
     various  pollutant  parameters present in the stream entering the
     clarifier unit.  The methods used in  determining  the  lime  and
     sodium sulfide requirements are shown in Table VIII-3 (page 336).

     LABOR

     Figure,VIII-14 (page 337) presents the man-hour requirements  for
     the   continuous   clarifier   system.   For  the  batch  system,
     maintenance labor is assumed to be negligible and operation labor
     is calculated from:
     (man-hours for operation) = 390 +
     ENERGY
(.975)   (Ibs.
      day)
lime  added  per
     The energy costs are calculated from
     pump horsepower requirements.

     Continuous Mode
    the  clarifier  and  sludge
     The  clarifier  horsepower  requirement is assumed to be constant
     over the hours of operation of the treatment system at a level of
     0.0000265 horsepower per 1 gph of flow influent to the clarifier.
     The sludge pumps are assumed to be operational for 5  minutes  of
     each  operational hour at a level of 0.00212 horsepower per 1 gph
     of sludge stream flow.

     Batch Mode

     The clarifier horsepower requirement is assumed to occur for  7.5
     minutes per operational hour at the following level:

          influent flow  1042 gph; 0.0048 hp/gph

          influent flow  1042 gph; 0.0096 hp/gph

     The  power  required  for the sludge pumps in the batch system is
     the same as that required for the sludge pumps in the  continuous
     system.

     Given the above requirements, operation and maintenance costs are
     calculated based on the following:
                                 308

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          $6.00 per man-hour +  10%  indirect  labor charge
          $41.26/ton of lime
          $0.284/pound of sodium sulfide
          $0.032/kilowatt-hour  of required electricity

Sulfide Precipitation - Clarification

This  technology  removes  dissolved  pollutants  by  the formation of
precipitates  by reaction with sodium  sulfide,  sodium  bisulfide,  or
ferrous sulfide and lime, and subsequent removal of the precipitate by
settling.   As discussed for chemical precipitation and clarification,
the addition  of chemicals, formation of precipitates, and  removal  of
the  precipitated  solids  from the  wastewater  stream are addressed
together in cost estimation because of  their  interrelationships  and
common equipment under some circumstances.
Investment  Cost.
precipitation and
precipitation  and
concrete and steel
to provide a least
waste characterist
precipitation and
  Capital  cost  estimation  procedures  for sulfide
clarification are identical to  those  for  chemical
  clarification.   Continuous treatment systems using
 construction and batch treatment systems are costed
 cost system for each flow  range  and  set  of  raw
ics.   Cost factors are also the same as for chemical
clarification.
Operation  and  Maintenance  Costs.  Costs estimated for the operation
and maintenance of a sulfide precipitation  and  clarification  system
are  also  identical  to  those  for chemical precipitation and clari-
fication except for the cost of treatment chemicals.   Lime  is  added
prior   to   sulfide  precipitation  to  achieve  an  alkaline  pH  of
approximately  8.5-9  and  this  precipitates   some   pollutants   as
hydroxides   or   calcium  salts.   Lime  consumption  based  on  both
neutralization and formation of precipitates is calculated to  provide
a 10% excess over stochiometric requirements.  Sulfide costs are based
on the addition of ferrous sulfate and sodium bisulfide (NaHS) to form
a   10   percent   excess   of  ferrous  sulfide  over  stoichiometric
requirements for precipitation.  Reagent additions are  calculated  as
shown  in  Table  VIII-4  (page  338)  .    Labor  and energy rates are
identical to those shown for chemical precipitation and clarification.

Multi-Media Filtration                  i

This technology removes suspended solids by filtering them  through  a
bed  of  particles  of  several  distinct size ranges.  As a polishing
treatment after chemical precipitation and  clarification  multi-media
filtration  improves the removal of precipitates and thereby improving
removal of the original dissolved pollutants.

Capital Cost.   The size of the multi-media filtration unit is based on
20 percent excess  flow  capacity  and  a  hydraulic  loading  of  0.5
                                 309

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ft2/gpm.   The capital cost, presented in Figure VIII-15 (page 339) as
a function  of  flow  rate,  includes  a  backwash  mechanism,  pumps,
controls,  media and installation.  Minimum costs are obtained using a
minimum filter surface area of 60 ft2.

Operation and Maintenance.  The costs  shown  in  Figure  VIII-15  for
operation   and   maintenance  includes  contributions  of  materials,
electricity and labor.  These curves  result  from  correlations  made
with  data  obtained  by  a  major  manufacturer.   Energy  costs  are
estimated to be 3 percent of total O&M.

Membrane Filtration

Membrane filtration includes addition  of  sodium  hydroxide  to  form
metal  precipitates  and  removal  of  the  precipitated  solids  on a
membrane  filter.   As  a  polishing  treatment,  it  minimizes  metal
solubility  and  very  effectively removes precipitated hydroxides and
sulfides.

Capital Cost.  Based on manufacturer's data, a factor of $52.60 per  1
gph flow rate to the membrane filter is used to estimate capital cost.
Capital cost includes installation.
                                   The operation and maintenance costs
Operation  and  Maintenance Cost.
for membrane filtration includeT

     1 )   Labor
     2)   Sodium Hydroxide Added
     3 >   Energy

Each of these contributing factors are discussed below.

     LABOR

     2 man-hours per day of operation are included.

     SODIUM HYDROXIDE ADDITION

     Sodium hydroxide is added to precipitate metals as hydroxides  or
to  insure  a  pH  favorable  to sulfide precipitation.  The amount of
sodium hydroxide required is based on equivalent  amounts  of  various
pollutant  parameters  present  in  the  stream  entering the membrane
filter.  The method used to determine the sodium hydroxide  demand  is
shown below:
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          POLLUTANT
ANaOH
          Chromium,  Total
          Copper
          Acidity
          Iron, DIS
          Zinc
          Cadmium
          Cobalt
          Manganese
          Aluminum
0.000508
0.000279
0.000175
0.000474
0.000268
0.000158
0.000301
0.000322
0.000076
(Sodium Hydroxide Per Pollutant,  Ib/day)  » ANaOH x Flow Rate
 (GPH)  x Pollutant Concentration (mg/1)

     ENERGY                '

     The horsepower required is as follows:

     2  1/2-horsepower mixers operating 34 minutes per operational hour

     2  1-horsepower pumps operating 37 minutes per operational hour

     T 20-horsepower pump operating 45 minutes per operational hour

Given the above requirements,  operation  and  maintenance  costs  are
calculated based on the following:

          $6.00 per man-hour + 10% indirect labor charge
          $0.11 per pound of sodium hydroxide required
          $0.032 per kilowatt-hour of energy required

Ultrafiltration                         i

Capital  Cost.   The  capital  cost  for ultrafiltration is calculated
using a correlation developed from data  supplied  by  a  major  manu-
facturer.   Figure VIII-16 (page 340) illustrates the results for this
correlation.

OPERATION AND MAINTENANCE COSTS

The unit is sized on the basis of a hydraulic loading of 1,430   I/day/
m2  of  surface area and an excess capacity factor of 1.2.  The  opera-
tion and maintenance costs are made up of  contributions from:

     1)   Labor                         ;
     2)   Membrane Replacement
     3)   Energy
                                 311

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 Each  of  these factors  are discussed below.

      LABOR

      Figure   VIII-17   (page   341)   shows   curves    of
      requirements  for  both maintenance  and  operation.

      MEMBRANE REPLACEMENT

      One filter  module is required  per  year for each 500
      day of  treated flow.

      ENERGY
the   man-hour
  gallons  per
     The power  requirements  based on  30.48  m  of pumphead yield  a   con-
     stant  horsepower value of  0.006  horsepower per  1  gph  flow to the
     ultrafiltration unit.

     Given the  above requirements, opeation and maintenance costs   are
     calculated based on  the following:

          $6.00 per man-hour + 10 percent indirect  labor charge
          $218/ultrafiltration module
          $0.032/kilowatt-hour of required  energy

Vacuum Filtration

Vacuum  filtration  is widely used to  reduce  the water  content  of  high
solids streams.  In the coil coating  industry, this technology  is  used
to dewatering sludge from clarifiers,  membrane filters  and  other waste
treatment units.

Capital Cost.   The vacuum filter is sized based on a  typical   loading
of 14.6 kg of influent solids per hour per  square meter of  filter  area
(3   Ibs/ft2-hr).   The  curves  of  cost   versus  flow  rate   at   TSS
concentrations  of 3 percent  and 5 percent are shown in  Figure   VIII-18
(page  342).    The  capital  cost  obtained   from  this curve includes
installation costs.

Operation and Maintenance Cost.

     LABOR

     The vacuum filtration subroutine may be run for  off-site  sludge
disposal   or   for   on-site  sludge  incineration.   On-site  sludge
incineration assumes a conveyor transport and reduced  operating  man-
hours  from those for off-site disposal.  The required operating hours
per year varies with both flow rate and  the  total  suspended  solids
concentration in the influent stream.  Figure VIII-19 (page 343) shows
                                 312

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the  variance of operating hours with flow rate and TSS concentration.
Maintenance labor for either sludge  disposal  mode  is  fixed  at  24
manhours per year.

     MATERIALS

     The cost of materials  and  supplies  needed  for  operation  and
maintenance includes belts, oil, grease, seals, and chemicals required
to  raise the total suspended solids to the vacuum filter.  The amount
of chemicals required {iron and alum) is  based  on  raising  the  TSS
concentration to the filter by 1 mg/1.  Costs of materials required as
a  function of flow rate and unaltered TSS concentrations is presented
in Figure VIII-20 (page 344).

     ENERGY

     Electrical costs needed to supply power for  pumps  and  controls
are presented in Figure VIII-21 (page 345).  Because the required pump
horsepower  depends on the influent TSS level, the costs are presented
as a function of flow rate and TSS level.

Contract Removal
___^^_____^^_^____

Sludge, waste oils, and in some  cases  concentrated  waste  solutions
frequently result from wastewater treatment processes.  Although these
may  be  disposed of on-site by incineration, landfill or reclamation,
they are most often removed on a contract basis for off-site disposal.
System cost estimates are based on contract  removal  of  sludges  and
waste  oils.   Where only small volumes of concentrated wastewater are
produced, contract-removal for off-site treatment  may  represent  the
most  costeffective  approach to water pollution abatement.  Estimates
of solution contract-haul costs are also provided by  this  subroutine
and  may  be  selected  in  place of on-site treatment on a least-cost
basis.

Capital Costs.  Capital investment for contract removal is zero.

Operating Costs.  Annual costs are estimated for contract  removal  of
total  waste  streams  or sludge and oil streams as specified in input
data.  Sludge and oil removal costs are further divided into  wet  and
dry  haulage  depending upon whether or not upstream sludge dewatering
is provided.  The use of wet haulage or of sludge dewatering  and  dry
haulage  is  based  on  least  cost as determined by annualized system
costs over a ten year period.  Wet haulage costs are  always  used  in
batch  treatment  systems  and when the volume of the sludge stream is
less than 100 gallons per day.

Both wet sludge haulage and total waste haulage  differ   in  cost  de-
pending  on the chemical composition of the waste removed.  Wastes are
                                 313

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classified as cyanide bearing, hexavalent chromium  bearing,
and assigned different haulage costs as shown below.
                           or  oily
     Waste Composition

    -0.05 mg/1 CN-
    -0.1 mg/1 Cr+6
     Oil & grease-TSS
     All others
Haulage Cost

$0.45/gallon
$0.20/gallon
$0.12/gallon
$0.16/gallon
Dry sludge haul costs are estimated at $0.12 gallon and 40% dry solids
in the sludge.

In-process Treatment and Control Components

Two  major  in-process control techniques have been identified for use
in  reducing  wastewater  pollutant  discharges  from   coil   coating
facilities.   Since  product  quench  water  constitutes a substantial
fraction of the total process wastewater discharge, use of  a  cooling
tower  to  recirculate this stream significantly reduces effluent flow
rates and pollutant loads.  Also,  cyanides  may  be  eliminated  from
process wastewater effluents by substitution of non-cyanide chromating
solutions.   Cost estimates are presented for cooling towers; however,
EPA did not develop specific cost estimates for substitution  of  non-
cyanide  chromating  solutions  because  these  costs  are highly site
specific and are not amenable to estimation on a general basis.
Quench water recirculation requires installation of
for the quench stream.
                  a  cooling  tower
Capital Costs.  The cooling towers were sized to provide a temperature
reduction  through  the  tower of approximately 5.6°C with an effluent
temperature 3.9°C above the ambient  wet  bulb  temperature.   Capital
costs  presented  in  Figure  VII1-22   (page  346)  are  based on data
supplied by a major manufacturer.  The smallest unit available is  for
10  gpm  flow.   For  flow rates less than  10 gpm, capital (as well as
operating and maintenance) costs are set to zero,  and  a  warning  is
printed.   The  three  distinct  curve  segments  correspond  to three
different cooling units which are required  to  produce  the  necessary
range of flow capacity.

Operation  and  Maintenance Costs.  Operation and maintenance expenses
include labor and electrical power.  Labor  is estimated at  252  hours
per year.

Figure  VIII-23   (page  347)  shows  the  electrical  energy costs for
operation of the pumps and fans for the cooling tower.
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Non-cyanide chromating solutions are available which  serve  the  same
function  as  the  cyanide bearing solutions at an approximately equal
cost; however, reports indicate that use of the non-cyanide  solutions
requires  closer  process  control  and  longer  residence time in the
chromating bath.  The costs of reagent  substitution,  therefore,  are
not  directly  calculable as reagent or fixed equipment costs, but are
highly  dependent  on  process  conditions   at   individual   plants.
Facilities  with  well-controlled  processes  may  be able to use non-
cyanide  solutions  with  little  or  no  cost  impact,  while  poorly
controlled  facilities  or  facilities with marginally sized equipment
could incur very high costs for major process revisions.  As a  result
of these considerations, no general cost estimates for this technology
are presented, and none are included in system cost estimates.

Summary  of  Treatment and Control Component Costs.  Example costs for
each of the treatment and control components discussed above  as  sup-
plied  to  process wastewater streams within the coil coating category
are presented in Tables VIII-5 through VIII-18 (pages 348-361).   Each
technology  is  provided  with  three  cost  levels  representative of
typical, low and high raw waste  flow  rates  encountered  within  the
category.

TREATMENT SYSTEM COST ESTIMATES         I
                                        i
This  section  presents  estimates  of  the  total  cost of wastewater
treatment and control systems  which  incorporate  the  treatment  and
control  components  discussed  above.  Median (typical),  low and high
flow rates  in the subcategory addressed are presented for  each   system
in order to provide an  indication of the range of costs to be incurred
in implementing each level of treatment;  All available flow data from
industry  data  collection  portfolios  were  used in defining median,
maximum and minimum raw waste flows, and flow breakdowns where streams
are  segregated  for treatment.  Raw waste characteristics were based on
sampling data as discussed  in Section V.

The  system  costs   include  component  costs  and   subsidiary   costs,
including engineering,  line segregation, admininstration,  and  interest
expenses  during  construction.   The   cost  estimates  for BPT systems
assume  that none of  the specified treatment and  control  measures  are
in   place,  so  that the presented costs represent total costs for the
systems.  Costs are presented for BAT systems  both   as  total   system
costs   and  as   incremental  costs   required to  modify  an  existing BPT
system  to achieve BAT.

System  Cost Estimates  (BPT)

This section  presents  the  system  cost estimates  for   the   BPT end-of-
pipe treatment  sytems.   Several  flow rates  are presented  for  each  case
to effectively  model  a wide spectrum of plant  sizes.
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Figure  IX-1 (page 400) shows the representative end-of-pipe treatment
for all three basis material subcategories.  The chemical oxidation of
cyanide and the chemical reduction of chromium are shown  as  optional
treatment  processes.  The use of either of these treatment components
depends on the production processes employed at the  plant.   For  the
purpose  of  the  BPT  system  cost  estimates,  cyanide oxidation was
assumed to be a required  treatment  process  only  for  the  aluminum
subcategory,  because  of  the  presence  of cyanide in the chromating
baths applied to aluminum.  Chromium reduction  was  included  in  the
system costs for all subcategories to treat hexavalent chromium wastes
from  the  chromic  acid  sealer  and conversion coating rinses, where
appropriate.

The costing assumptions for each component  of  the  BPT  system  were
discussed  above  under Technology Costs and Assumptions.  In addition
to these components, contractor oil and sludge removal was included in
all cost estimates.

Tables VIII-19 through  VIII-21  (pages  362-364)  present  costs  for
example  BPT  treatment  system  influent  flow rates.  The basic cost
elements used  in  preparing  these  tables  are  the  same  as  those
presented for the individual technologies:  investment, annual capital
cost, annual depreciation, annual operation and maintenance cost (less
energy cost), energy cost, and total annual cost.  These elements were
discussed in detail earlier in this section.

Cost  computations  were  based on selection of a least cost treatment
system.  This procedure calculated the costs  for  a  batch  treatment
system,  a  continuous  treatment  system, and haulage of the complete
waste water flow over a 10 year comparison period; the least expensive
system was then selected for presentation in the system cost tables.

The various investment costs assume that the treatment system must  be
specially  constructed  and  include  all  subsidiary  costs discussed
previously.   Operation  and  maintenance  costs   assume   continuous
operation, 24 hours a day, 5 days per week, for 52 weeks per year.

System Cost Estimates (BAT Level I)

System  cost  estimates for adding a multimedia filter to the BPT end-
of-pipe system were developed to provide BAT Level  I  treatment  cost
estimates.   A schematic of this end-of-pipe system is shown in Figure
X-1 (page 416).  The costing assumptions  for  the  multimedia  filter
were discussed earlier.

Tables  VIII-22  through  VIII-24  (pages 365-367) present example BAT
Level I treatment costs for construction  of  the  entire  end-of-pipe
system.   These costs represent anticipated expenditures to attain BAT
Level I for a plant  with  no  treatment  in  place.   Tables  VII1-25
                                 316

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through   VIII-27  (pages  368-370)  present  the  predicted  cost  of
installing a multimedia filter at a plant  which  already  has  a  BPT
treatment  system  in  place.   Operating  and  maintenance as well as
energy costs presented in these tables apply to  expenditures  arising
from  operation  of  the  entire  end-of-pipe  system  (including  the
previously installed BPT components).

System Cost Estimates (BAT Level II)

The BAT  Level  II  alternative  calls  for  reduction  of  the  plant
discharge  flow  rate  by  using  in-plant technology-recirculation of
quench waters.

Recirculation of quench water  significantly  reduces  the  volume  of
waste  water  discharged  by  a  typical coil coating plant.  Costs of
installing and operating a cooling  tower  were  calculated  based  on
total quench water recirculation.  Design and cost assumptions for the
cooling tower were discussed previously.

For  the  aluminum  subcategory,  BAT  Level  II in-process technology
includes substitution of non-cyanide  chromating  solutions  in  cases
where   cyanide  solutions   are  currently  being  used.   This  would
eliminate  the  require  for  cyanide  treatment;   however,   cyanide
oxidation  costs  are  included  for  BAT  Levels  II  and III for the
aluminum subcategory to be used as a option.  Cyanide oxidation  is not
used for either the steel or galvanized  steel  subcategories  because
cyanide  was not present in  the raw waste characteristics presented  in
Section V.

Tables VIII-28 through VIII-30  (pages 371-373)  present  example  cost
data  for  construction  and operations  of  BAT  Level   II treatment
facilities for a plant with  no  existing waste water treatment.   Figure
X-2  (page 417) depicts   the  components  of  the  end-of-pipe  system.
Quench water  recirculation are  integrated within the process line.

Tables  VIII-31  through VIII-33  (pages 374-376) present cost  data for
upgrading treatment  facilities  to  BAT  Level   II  for  a  plant  with
existing  BPT  equipment.  The operating and maintenance costs  in these
tables  include operation of  the existing  BPT   equipment   as   well  as
those    components   added  to   reach  BAT  Level   II.   The  treatment
components assumed  to  be  in  place  for BPT  include  chromium  reduction,
oil  skimming,  and  clarification with  sludge bed dewatering.  The added
components   to  meet  BAT Level II  include a multi-media filter  on the
end-of-pipe  system and quench water  recirculation  systems  integrated
within  the production  process.

Summation  of BPT system  costs with the  costs  for system  upgrading  to
BAT  Level  II  do  not equal  the  costs   presented   in   this   section  for
construction  of  a complete BAT Level  II  system.  This  is a result  of
                                  317

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 the clarifier-sludge bed  sizing  requirements.    The  BPT  clarifier-
 sludge bed combination must be sized to handle a much larger flow rate
 than  the  equivalent clarifier-sludge bed system that is designed for
 the reduced BAT Level II flow.   A similar result occurs when comparing
 BAT Level I and Level II costs.   Reduced multi-media  filter  size  is
 possible  when  the treatment system is designed to handle the reduced
 flow of Level  II as opposed to the higher flow of Level I.

 System Cost Estimates (BAT Level III)

 The BAT Level  III treatment alternative is very  similar  to  the  BAT
 Level II system discussed above.   The  only difference is that effluent
 polishing  on   the  end-of-pipe   system  for  BAT Level III  substitutes
 ultrafiltration for multi-media  filtration  (Figure  X-3,   page  418).
 The  Level III alternative also  uses the inplant technologies of  Level
 II.    The  costing  assumptions   for  ultrafiltration  were  presented
 previously under "Technology Costs and Assumptions".

 Tables  VIII-34  through  VIII-36  (pages 377-379)  present  costs  for  a
 Level III system designed for plants  with no  existing  waste  water
 treatment.   Tables  VIII-37  through   VIII-39 (pages 380-382)  present
 costs for installation of components necessary to upgrade  existing BPT
 treatment systems to Level  III and" to  operate the entire system.

 System Cost Estimates - (New Sources)

 The suggested  treatment alternatives for NSPS Levels  I  and  II   are
 identical  to the treatment  alternatives for existing  source BAT Levels
 II   and  ill.    These  costs were presented  in  Tables VII1-28  through
 VIII-37.   NSPS Level  III  is similar to BAT Level  III  except  that   the
 clarifler  is   replaced  by  membrane   filtration  for NSPS Level  III.
 Figure XI-3  (page 445)  presents  a schematic of this system,  and  costs
 are  presented in Tables  VIII-40  through VIII-42  (pages  383-385).   The
 system costs include  quench water  recirculation   costs  as  discussed
 previously  for BAT Level  II.

 Use of  Cost  Estimation  Results

 Cost   estimates  presented  in the  tables  in this section  are rement  and
 control  equivalent to   the  specified  levels.    They will  not,  in
 general,   correspond  precisely   to cost  experience  at  any individual
plant.   Specific  plant  conditions such as  age, location, plant  layout
or present production and treatment practices may  yield  costs  which
are   either  higher  or  lower  than  the presented costs.  Because  the  BPT
costs shown  are  total system  costs  and do  not assume  any treatment  in
place,    it    is   probable   that  most   plants  will   require   smaller
expenditures to  reach the   specified   levels  of  control   from  their
present  status.
                                 318

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The  actual  costs  of  installing  and  operating  a  BPT system at a
particular plant may be substantially lower than the tabulated values.
Reductions in investment and operating costs are possible  in  several
areas.   Design  and  installation costs may be reduced by using plant
workers.  Equipment  costs  may  be  reduced  by  using  or  modifying
existing   equipment   instead   of   purchasing  all  new  equipment.
Application of an excess capacity factor, which increases the size  of
most  equipment  foundation  costs  could  be  reduced  if an existing
concrete pad or floor can be utilized.   Equipment  size  requirements
may  be  reduced  by  the  ease  of  treatment  (for  example, shorter
retention time) of particular waste streams.  Substantial reduction in
both investment and operating cost may be achieved if a plant  reduces
its water use rate below that assumed in costing.

ENERGY AND NON-WATER QUALITY ASPECTS

Energy Aspects                          I

Energy  aspects  of  the  wastewater treatment processes are  important
because of the impact of energy use on our natural  resources  and  on
the  economy.   Electrical  power and fuel requirements  (coal, oil, or
gas) are  listed in units of kilowatt hours per ton of dry  solids  for
sludge  and  solids  handling.   Specific energy uses are noted  in the
"Remarks" column.

Energy  requirements are generally low, although evaporation can  be  an
exception  if no waste heat is available at  the plant.   If evaporation
is used to avoid discharge of  pollutants,   the  influent  water rate
should  be  minimized.   For  example,   an upstream reverse osmosis or
ultrafiltration unit can drastically reduce  the flow of  wastewater  to
an evaporation device.

Non-Water Quality Aspects

It   is  important   to  consider the  impact of each  treatment process on
air,  noise, and radiation pollution of  the  environment  to preclude  the
development of a more  adverse environmental  impact.

In general, none of  the  liquid   handling processes   causes   air pol-
lution.   With  sulfide  precipitation,  however,  the  potential exists  for
evolution of  hydrogen  sulfide,  a  toxic gas.   Proper  control of pH in
treatment eliminates  this problem.  Alkaline chlorination  for  cyanide
destruction   and   chromium  reduction   using  sulfur  dioxide  also have
potential atmospheric  emissions.  With  proper  design   and  operation,
however,   air  pollution  impacts  are   eliminated.    Incineration   of
sludges or solids  can  cause significant  air pollution   which   must   be
controlled   by    suitable    bag   houses,    scrubbers  or   stack  gas
precipitators  as  well  as proper  incinerator operation and  maintenance.
None of the wastewater treatment processes  causes  objectionable  noise
                                  319

-------
and  none of the treatment processes has any potential for radioactive
radiation hazards.

The processes for treating the wastewaters from this category  produce
considerable  volumes  of  sludges.   In  order  to  ensure  long-term
protection  of  the  environment  from  harmful  sludge  constituents,
special  consideration  of  disposal  sites should be made by RCRA and
municipal authorities where applicable.
                                 320

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                        TABLE VIII-1
                COST PROGRAM STREAM PARAMETERS
Parameter, Units

Flow, MGD
pHf pH units
Turbidity, Jackson Units
Temperature, degree C
Dissolved Oxygen, mg/1
Residual Chlorine, mg/1
Acidity, mg/1 CaCOj
Alkalinity, mg/1 CaC03
Ammonia, mg/1
Biochemical Oxygen Demand mg/1
Color, Chloroplatinate units
Sulfide, mg/1
Cyanides, "mg/1
"Kjeldahl Nitrogen, mg/1
Pnenols, mg/1
Conductance, micromhos/cm .
Total Solids, mg/1
Total Suspended Solids, rag/1
Settleable Solids, rag/1
Aluminum, mg/1
Barium, mg/1
Cadmium, mg/1
Calcium, mg/1
Chromium, Total, mg/1
Copper, mg/1
Fluoride, mg/1
Iron, Total, mg/1
Lead, mg/1
Magnesium, mg/1
Molybdenum, mg/1
Total Volatile Solids, mg/1
Parameter, Units

Oil, Grease, mg/1
Hardness, mg/1 CaC03
Chemical.Oxygen Demand, mg/1
Algicides, mg/1
Total Phosphates, mg/1
Polychlorobiphenyls, mg/1
Potassium, mg/1
Silica, mg/1
Sodium, mg/1
Sulfate, mg/1
Sulfite, mg/1
Titanium, mg/1
Zinc, mg/1
Arsenic, mg/1
Boron, mg/1
Iron, Dissolved,- mg/1
Mercury, mg/1
Nickel, rog/1
Nitrate, mg/1
Selenium, mg/1
Silver, mg/1
Strontium, mg/1
Surfactants, mg/1
Beryllium, mg/1
Plasticizers, mg/1
Antimony, mg/1
Bromide, mg/1
Cobalt, mg/1
Thallium, mg/1
Tin, mg/1
Chromium, Hexavalent,  mg/1
                                 321

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                            SIMPLIFIED LOGIC DIAGRAM
                        SYSTEM COST ESTIMATION PROGRAM
NON-RECYCLE
  SYSTEMS
                          INPUT
                          A)    RAW WASTE DESCRIPTION
                          B)    SYSTEM DESCRIPTION
                          C)    "DECISION" PARAMETERS
                          D)    COST FACTORS
                          PROCESS CALCULATIONS
                          A)   PERFORMANCE - POLLUTANT
                              PARAMETER EFFECTS
                          B)   EQUIPMENT SIZE
                          C)   PROCESS COST
                                          (RECYCLE SYSTEMS)
CONVERGENCE
A)   POLLUTANT PARAMETER
     TOLERANCE CHECK
                                             (NOT WITHIN
                                             TOLERANCE LIMITS)
                                          (WITHIN TOLERANCE LIMITS)
                       COST CALCULATIONS
                       A)   SUM INDIVIDUAL PROCESS
                            COSTS
                       B)   ADD SUBSIDIARY COSTS
                       C)   ADJUST TO DESIRED DOLLAR BASE
                        OUTPUT
                        A)   STREAM DESCRIPTIONS-
                             COMPLETE SYSTEM
                        B)   INDIVIDUAL PROCESS SIZE AND
                             COSTS
                        C)   OVERALL SYSTEM INVESTMENT
                             AND ANNUAL COSTS
                    FIGURE VIII-1.  COST ESTIMATION PROGRAM
                                         322

-------
                CHEMICAL
                ADDITION
RAW WASTE
(FLOW. TSS. LEAD
ZINC, ACIDITY)

CHEMICAL
PRECIPITATION
C^>


-^-LJ-XJ-I
SEDIMENTATION
^~~*asSS8j&l^ttfi'
EFFL

                      RECYCLE
                                                         SLUDGE
                                                         (CONTRACTOR
                                                          REMOVED)
       FIGURE VIII-2.  SIMPLE WASTE TREATMENT SYSTEM
                                    323

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                           TABLE VIII-2

                  WASTEWATER SAMPLING FREQUENCY
Waste Water Discharge
    (liters/day)

      0 - 37,850

 37,850 - 189,250

189,250 - 378,500

378,500 - 946,250

946,250+
Sampling Frequency


once per month

twice per month

once per month

twice per week

thrice per week
                              324

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